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In a Cross-Site Request Forgery attack, untrusted web content causes browsers to send authenticated requests to web servers which use cookies for authentication. While the web content is prevented from reading the request's response due to the Cross-Origin Request Sharing (CORS) protocol, an attacker may be able to cause side effects in the server ("CSRF" attack), or learn something about the response via timing analysis ("XS-Search" attack).
Apollo Server has a built-in feature which prevents CSRF and XS-Search attacks: it refuses to process GraphQL requests that could possibly have been sent by a spec-compliant web browser without a protective "preflight" step. See Apollo Server's docs for more details on CORS, CSRF attacks, and Apollo Server's CSRF prevention feature.
This feature is fully effective against attacks carried out against users of spec-compliant browsers. Unfortunately, a major browser introduced a bug in 2025 which meant in certain cases, it failed to follow the CORS spec. The browser's maintainers have already committed to fixing the bug and making the browser spec-compliant again.
Even with this bug, Apollo Server's CSRF prevention feature blocks "side effect" CSRF attacks: Apollo Server will still correctly refuse to execute mutations in requests that were not preflighted. However, some specially crafted authenticated GraphQL queries can be issued across origins without preflight in buggy versions of this browser, allowing for XS-Search attacks: an attacker can analyze response times to learn facts about the responses to requests such as whether fields return null or approximately how many list entries are returned from fields.
GraphQL servers are only vulnerable if they rely on cookies (or HTTP Basic Auth) for authentication.
Patches
The vulnerability is patched in @apollo/server v5.5.0. This release contains a single change: GraphQL requests sent in HTTP GET requests which contain a Content-Type header naming a type other than application/json are rejected. (GET requests with no Content-Type are allowed.) This change prevents XS-Search attacks even in browsers which are non-compliant in ways similar to this browser.
There are no known cases where GraphQL apps depend on the ability of clients to send non-empty Content-Type headers with GET requests other than application/json, so this change has not been made configurable; if this change breaks a use case, file an issue and more configurability can be added.
Apollo is not currently providing a patch for previous major versions of Apollo Server, which are all end-of-life.
Workarounds
If upgrading is not possible, this particular browser's bug can be mitigated by preventing any HTTP request with a Content-Type header containing message/ from reaching Apollo Server (e.g. in a proxy or middleware).
For example, when using Apollo Server's Express integration, something like this can be placed before attaching expressMiddleware to the app:
app.use((req,res,next)=>{for(leti=0;i<req.rawHeaders.length-1;i+=2){if(req.rawHeaders[i].toLowerCase()==='content-type'&&req.rawHeaders[i+1].includes('message/')){returnres.status(415).json({error: 'Content-Type not allowed'});}}next();});
While the patch prevents a broader class of similar issues, the only known way to exploit this vulnerability is against a particular browser which currently plans to ship a fix in May 2026. If it is already past June 2026 and this vulnerability has not been addressed yet, it is likely that the system is not currently vulnerable. Upgrading to the latest version of Apollo Server is still recommended for the broader protection.
Resources
The browser bug causes a similar vulnerability in Apollo Router; see GHSA-hff2-gcpx-8f4p
Apollo Server now rejects GraphQL GET requests which contain a Content-Type header other than application/json (with optional parameters such as ; charset=utf-8). Any other value is now rejected with a 415 status code.
(GraphQL GET requests without a Content-Type header are still allowed, though they do still need to contain a non-empty X-Apollo-Operation-Name or Apollo-Require-Preflight header to be processed if the default CSRF prevention feature is enabled.)
This improvement makes Apollo Server's CSRF more resistant to browsers which implement CORS in non-spec-compliant ways. Apollo is aware of one browser which as of March 2026 has a bug which allows an attacker to circumvent Apollo Server's CSRF prevention feature to carry out read-only XS-Search-style CSRF attacks. The browser vendor is in the process of patching this vulnerability; upgrading Apollo Server to v5.5.0 mitigates this vulnerability.
If your server uses cookies (or HTTP Basic Auth) for authentication, Apollo encourages you to upgrade to v5.5.0.
This is technically a backwards-incompatible change. Apollo is not aware of any GraphQL clients which provide non-empty Content-Type headers with GET requests with types other than application/json. If your use case requires such requests, please file an issue and we may add more configurability in a follow-up release.
The default configuration of startStandaloneServer was vulnerable to denial of service (DoS) attacks through specially crafted request bodies with exotic character set encodings.
In accordance with RFC 7159, we now only accept request bodies encoded in UTF-8, UTF-16 (LE or BE), or UTF-32 (LE or BE).
Any other character set will be rejected with a 415 Unsupported Media Type error.
Note that the more recent JSON RFC, RFC 8259, is more strict and will only allow UTF-8.
Since this is a minor release, we have chosen to remain compatible with the more permissive RFC 7159 for now.
In a future major release, we may tighten this restriction further to only allow UTF-8.
If you were not using startStandaloneServer, you were not affected by this vulnerability.
Generally, please note that we provide startStandaloneServer as a convenience tool for quickly getting started with Apollo Server.
For production deployments, we recommend using Apollo Server with a more fully-featured web server framework such as Express, Koa, or Fastify, where you have more control over security-related configuration options.
#816151acbeb Thanks @jerelmiller! - Fix an issue where some bundlers would fail to build because of the dynamic import for the optional peer dependency on @yaacovcr/transform introduced in @apollo/server 5.1.0. To provide support for the legacy incremental format, you must now provide the legacyExperimentalExecuteIncrementally option to the ApolloServer constructor.
If the legacyExperimentalExecuteIncrementally option is not provided and the client sends an Accept header with a value of multipart/mixed; deferSpec=20220824, an error is returned by the server.
#814880a1a1a Thanks @jerelmiller! - Apollo Server now supports the incremental delivery protocol (@defer and @stream) that ships with graphql@17.0.0-alpha.9. To use the current protocol, clients must send the Accept header with a value of multipart/mixed; incrementalSpec=v0.2.
Upgrading to 5.1 will depend on what version of graphql you have installed and whether you already support the incremental delivery protocol.
Apollo Server v5 has very few breaking API changes. It is a small upgrade focused largely on adjusting which versions of Node.js and Express are supported.
Read our migration guide for more details on how to update your app.
Dropped support for Node.js v14, v16, and v18, which are no longer under long-term support from the Node.js Foundation. Apollo Server 5 supports Node.js v20 and later; v24 is recommended. Ensure you are on a non-EOL version of Node.js before upgrading Apollo Server.
Dropped support for versions of the graphql library older than v16.11.0. (Apollo Server 4 supports graphqlv16.6.0 or later.) Upgrade graphql before upgrading Apollo Server.
Express integration requires a separate package. In Apollo Server 4, you could import the Express 4 middleware from @apollo/server/express4, or you could import it from the separate package @as-integrations/express4. In Apollo Server 5, you must import it from the separate package. You can migrate your server to the new package before upgrading to Apollo Server 5. (You can also use @as-integrations/express5 for a middleware that works with Express 5.)
Usage Reporting, Schema Reporting, and Subscription Callback plugins now use the Node.js built-in fetch implementation for HTTP requests by default, instead of the node-fetch npm package. If your server uses an HTTP proxy to make HTTP requests, you need to configure it in a slightly different way. See the migration guide for details.
The server started with startStandaloneServer no longer uses Express. This is mostly invisible, but it does set slightly fewer headers. If you rely on the fact that this server is based on Express, you should explicitly use the Express middleware.
The experimental support for incremental delivery directives @defer and @stream (which requires using a pre-release version of graphql v17) now explicitly only works with version 17.0.0-alpha.2 of graphql. Note that this supports the same incremental delivery protocol implemented by Apollo Server 4, which is not the same protocol in the latest alpha version of graphql. As this support is experimental, we may switch over from "only alpha.2 is supported" to "only a newer alpha or final release is supported, with a different protocol" during the lifetime of Apollo Server 5.
Apollo Server is now compiled by the TypeScript compiler targeting the ES2023 standard rather than the ES2020 standard.
Apollo Server 5 responds to requests with variable coercion errors (eg, if a number is passed in the variables map for a variable declared in the operation as a String) with a 400 status code, indicating a client error. This is also the behavior of Apollo Server 3. Apollo Server 4 mistakenly responds to these requests with a 200 status code by default; we recommended the use of the status400ForVariableCoercionErrors: true option to restore the intended behavior. That option now defaults to true.
The unsafe precomputedNonce option to landing page plugins (which was only non-deprecated for 8 days) has been removed.
Patch Changes
There are a few other small changes in v5:
#80765b26558 Thanks @valters! - Fix some error logs to properly call logger.error or logger.warn with this set. This fixes errors or crashes from logger implementations that expect this to be set properly in their methods.
#7515100233a Thanks @trevor-scheer! - ApolloServerPluginSubscriptionCallback now takes a fetcher argument, like the usage and schema reporting plugins. The default value is Node's built-in fetch.
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This PR contains the following updates:
^4.10.0→^5.0.0Apollo Server: Browser bug allows for bypass of XS-Search (read-only Cross-Site Request Forgery) prevention
GHSA-9q82-xgwf-vj6h
More information
Details
Impact
In a Cross-Site Request Forgery attack, untrusted web content causes browsers to send authenticated requests to web servers which use cookies for authentication. While the web content is prevented from reading the request's response due to the Cross-Origin Request Sharing (CORS) protocol, an attacker may be able to cause side effects in the server ("CSRF" attack), or learn something about the response via timing analysis ("XS-Search" attack).
Apollo Server has a built-in feature which prevents CSRF and XS-Search attacks: it refuses to process GraphQL requests that could possibly have been sent by a spec-compliant web browser without a protective "preflight" step. See Apollo Server's docs for more details on CORS, CSRF attacks, and Apollo Server's CSRF prevention feature.
This feature is fully effective against attacks carried out against users of spec-compliant browsers. Unfortunately, a major browser introduced a bug in 2025 which meant in certain cases, it failed to follow the CORS spec. The browser's maintainers have already committed to fixing the bug and making the browser spec-compliant again.
Even with this bug, Apollo Server's CSRF prevention feature blocks "side effect" CSRF attacks: Apollo Server will still correctly refuse to execute mutations in requests that were not preflighted. However, some specially crafted authenticated GraphQL queries can be issued across origins without preflight in buggy versions of this browser, allowing for XS-Search attacks: an attacker can analyze response times to learn facts about the responses to requests such as whether fields return null or approximately how many list entries are returned from fields.
GraphQL servers are only vulnerable if they rely on cookies (or HTTP Basic Auth) for authentication.
Patches
The vulnerability is patched in
@apollo/serverv5.5.0. This release contains a single change: GraphQL requests sent in HTTPGETrequests which contain aContent-Typeheader naming a type other thanapplication/jsonare rejected. (GETrequests with noContent-Typeare allowed.) This change prevents XS-Search attacks even in browsers which are non-compliant in ways similar to this browser.There are no known cases where GraphQL apps depend on the ability of clients to send non-empty
Content-Typeheaders with GET requests other thanapplication/json, so this change has not been made configurable; if this change breaks a use case, file an issue and more configurability can be added.Apollo is not currently providing a patch for previous major versions of Apollo Server, which are all end-of-life.
Workarounds
If upgrading is not possible, this particular browser's bug can be mitigated by preventing any HTTP request with a
Content-Typeheader containingmessage/from reaching Apollo Server (e.g. in a proxy or middleware).For example, when using Apollo Server's Express integration, something like this can be placed before attaching
expressMiddlewareto theapp:While the patch prevents a broader class of similar issues, the only known way to exploit this vulnerability is against a particular browser which currently plans to ship a fix in May 2026. If it is already past June 2026 and this vulnerability has not been addressed yet, it is likely that the system is not currently vulnerable. Upgrading to the latest version of Apollo Server is still recommended for the broader protection.
Resources
The browser bug causes a similar vulnerability in Apollo Router; see GHSA-hff2-gcpx-8f4p
Severity
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:NReferences
This data is provided by the GitHub Advisory Database (CC-BY 4.0).
Release Notes
apollographql/apollo-server (@apollo/server)
v5.5.0Compare Source
Minor Changes
#8191⚠️ SECURITY
ada1200Thanks @glasser! -@apollo/server/standalone:Apollo Server now rejects GraphQL
GETrequests which contain aContent-Typeheader other thanapplication/json(with optional parameters such as; charset=utf-8). Any other value is now rejected with a 415 status code.(GraphQL
GETrequests without aContent-Typeheader are still allowed, though they do still need to contain a non-emptyX-Apollo-Operation-NameorApollo-Require-Preflightheader to be processed if the default CSRF prevention feature is enabled.)This improvement makes Apollo Server's CSRF more resistant to browsers which implement CORS in non-spec-compliant ways. Apollo is aware of one browser which as of March 2026 has a bug which allows an attacker to circumvent Apollo Server's CSRF prevention feature to carry out read-only XS-Search-style CSRF attacks. The browser vendor is in the process of patching this vulnerability; upgrading Apollo Server to v5.5.0 mitigates this vulnerability.
If your server uses cookies (or HTTP Basic Auth) for authentication, Apollo encourages you to upgrade to v5.5.0.
This is technically a backwards-incompatible change. Apollo is not aware of any GraphQL clients which provide non-empty
Content-Typeheaders withGETrequests with types other thanapplication/json. If your use case requires such requests, please file an issue and we may add more configurability in a follow-up release.See advisory GHSA-9q82-xgwf-vj6h for more details.
v5.4.0Compare Source
Minor Changes
d25a5bdThanks @phryneas! -@apollo/server/standalone:The default configuration of
startStandaloneServerwas vulnerable to denial of service (DoS) attacks through specially crafted request bodies with exotic character set encodings.In accordance with RFC 7159, we now only accept request bodies encoded in UTF-8, UTF-16 (LE or BE), or UTF-32 (LE or BE).
Any other character set will be rejected with a
415 Unsupported Media Typeerror.Note that the more recent JSON RFC, RFC 8259, is more strict and will only allow UTF-8.
Since this is a minor release, we have chosen to remain compatible with the more permissive RFC 7159 for now.
In a future major release, we may tighten this restriction further to only allow UTF-8.
If you were not using
startStandaloneServer, you were not affected by this vulnerability.Generally, please note that we provide
startStandaloneServeras a convenience tool for quickly getting started with Apollo Server.For production deployments, we recommend using Apollo Server with a more fully-featured web server framework such as Express, Koa, or Fastify, where you have more control over security-related configuration options.
v5.3.0Compare Source
Minor Changes
#8062
8e54e58Thanks @cristunaranjo! - Allow configuration of graphql execution options (maxCoercionErrors)#8014
26320bcThanks @mo4islona! - Exposegraphqlvalidation options.v5.2.0Compare Source
Minor Changes
#8161
51acbebThanks @jerelmiller! - Fix an issue where some bundlers would fail to build because of the dynamic import for the optional peer dependency on@yaacovcr/transformintroduced in@apollo/server5.1.0. To provide support for the legacy incremental format, you must now provide thelegacyExperimentalExecuteIncrementallyoption to theApolloServerconstructor.If the
legacyExperimentalExecuteIncrementallyoption is not provided and the client sends anAcceptheader with a value ofmultipart/mixed; deferSpec=20220824, an error is returned by the server.v5.1.0Compare Source
Minor Changes
#8148
80a1a1aThanks @jerelmiller! - Apollo Server now supports the incremental delivery protocol (@deferand@stream) that ships withgraphql@17.0.0-alpha.9. To use the current protocol, clients must send theAcceptheader with a value ofmultipart/mixed; incrementalSpec=v0.2.Upgrading to 5.1 will depend on what version of
graphqlyou have installed and whether you already support the incremental delivery protocol.v5.0.0Compare Source
BREAKING CHANGES
Apollo Server v5 has very few breaking API changes. It is a small upgrade focused largely on adjusting which versions of Node.js and Express are supported.
Read our migration guide for more details on how to update your app.
graphqllibrary older thanv16.11.0. (Apollo Server 4 supportsgraphqlv16.6.0or later.) Upgradegraphqlbefore upgrading Apollo Server.@apollo/server/express4, or you could import it from the separate package@as-integrations/express4. In Apollo Server 5, you must import it from the separate package. You can migrate your server to the new package before upgrading to Apollo Server 5. (You can also use@as-integrations/express5for a middleware that works with Express 5.)fetchimplementation for HTTP requests by default, instead of thenode-fetchnpm package. If your server uses an HTTP proxy to make HTTP requests, you need to configure it in a slightly different way. See the migration guide for details.startStandaloneServerno longer uses Express. This is mostly invisible, but it does set slightly fewer headers. If you rely on the fact that this server is based on Express, you should explicitly use the Express middleware.@deferand@stream(which requires using a pre-release version ofgraphqlv17) now explicitly only works with version17.0.0-alpha.2ofgraphql. Note that this supports the same incremental delivery protocol implemented by Apollo Server 4, which is not the same protocol in the latest alpha version ofgraphql. As this support is experimental, we may switch over from "onlyalpha.2is supported" to "only a newer alpha or final release is supported, with a different protocol" during the lifetime of Apollo Server 5.variablesmap for a variable declared in the operation as aString) with a 400 status code, indicating a client error. This is also the behavior of Apollo Server 3. Apollo Server 4 mistakenly responds to these requests with a 200 status code by default; we recommended the use of thestatus400ForVariableCoercionErrors: trueoption to restore the intended behavior. That option now defaults to true.precomputedNonceoption to landing page plugins (which was only non-deprecated for 8 days) has been removed.Patch Changes
There are a few other small changes in v5:
#8076
5b26558Thanks @valters! - Fix some error logs to properly calllogger.errororlogger.warnwiththisset. This fixes errors or crashes from logger implementations that expectthisto be set properly in their methods.#7515
100233aThanks @trevor-scheer! - ApolloServerPluginSubscriptionCallback now takes afetcherargument, like the usage and schema reporting plugins. The default value is Node's built-in fetch.Updated dependencies [
100233a]:Configuration
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