CVE-2026-23897: Apollo Server is vulnerable to denial of service with `startStandaloneServer`
Impact
The default configuration of startStandaloneServer from @apollo/server/standalone is vulnerable to Denial of Service (DoS) attacks through specially crafted request bodies with exotic character set encodings.
This issue does not affect users that use @apollo/server as a dependency for integration packages, like @as integrations/express5 or @as-integrations/next, only direct usage of startStandaloneServer.
Who is impacted
Users directly using startStandaloneServer from @apollo/server/standalone.
This issue affects Apollo Server from v5.0.0 through v5.3.x.
It also affects all releases of the end-of-life major versions v4, v3, and v2. Although Apollo Server v4 is EOL and Apollo no longer commits to providing support or updates for it, a fix for it was released in v4.13.0. Apollo Server v3 and v2 are no longer updated, as they have been EOL since 2024 and 2023 respectively.
Patches
Patches for this issue are released as @apollo/server versions 5.4.0 and 4.13.0.
In accordance with RFC 7159, these versions 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 (https://datatracker.ietf.org/doc/html/rfc8259#section-8.1), 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, the restriction may be tightened further to only allow UTF-8.
Workarounds
Users of apollo-server v2 or v3 that cannot upgrade for some reason could switch from the standalone apollo-server package to an integration package like apollo-server-express or apollo-server-koa and set up their own server. Please note that these old packages are generally EOL and do not receive any more support or bug fixes. This can only be seen as a short-term workaround. Updating to @apollo/server v5 should be a priority.
Other sources
Apollo Server is an open-source, spec-compliant GraphQL server that's compatible with any GraphQL client, including Apollo Client. In versions from 2.0.0 to 3.13.0, 4.2.0 to before 4.13.0, and 5.0.0 to before 5.4.0, the default configuration of startStandaloneServer from @apollo/server/standalone is vulnerable to denial of service (DoS) attacks through specially crafted request bodies with exotic character set encodings. This issue does not affect users that use @apollo/server as a dependency for integration packages, like @as-integrations/express5 or @as-integrations/next, only direct usage of startStandaloneServer.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/@apollo/serverto a version that resolves this vulnerability.Fixed in 5.4.0 - Upgrade
Upgrade
npm/@apollo/serverto a version that resolves this vulnerability.Fixed in 4.13.0 - Upgrade
Upgrade
@apollo/serverto a version that resolves this vulnerability.Fixed in 5.4.0 - Upgrade
Upgrade
@apollo/serverto a version that resolves this vulnerability.Fixed in 4.13.0 - Compensating control
Avoid using the vulnerable default configuration of startStandaloneServer from @apollo/server/standalone; instead, switch from the standalone apollo-server package to an integration package (e.g., apollo-server-express or apollo-server-koa) and set up their own server.
Event History
Frequently Asked Questions
What is the severity of CVE-2026-23897?
CVE-2026-23897 is classified as a denial of service (DoS) vulnerability.
How do I fix CVE-2026-23897?
To fix CVE-2026-23897, update to versions 5.4.0 or later for @apollo/server, or 4.13.0 or later for earlier versions.
Which versions of @apollo/server are affected by CVE-2026-23897?
CVE-2026-23897 affects @apollo/server versions between 5.0.0 and 5.4.0, and also versions between 4.2.0 and 4.13.0.
Does CVE-2026-23897 affect users of apollo-server?
Yes, CVE-2026-23897 affects versions of apollo-server between 2.0.0 and 3.13.0.
What is the main risk associated with CVE-2026-23897?
The main risk associated with CVE-2026-23897 is that it can lead to a denial of service through specially crafted request bodies.