CVE-2026-23897 Apollo Server is vulnerable to denial of service with `startStandaloneServer`
Attackers can cause denial of service in Apollo Server standalone mode via crafted request bodies with exotic encodings.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-23897?
CVE-2026-23897 is a high-severity denial of service vulnerability in apollographql apollo-server, published on 4 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-1333
Which versions are affected by CVE-2026-23897?
6 open source packages ship an affected version, including apollo-server and @apollo/server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
apollo-server npm | From 2.0.0 to 3.13.0 | None |
apollo-server npm | From 2.0.0 to 3.13.0 | None |
@apollo/server npm | From 4.2.0 | 4.13.0 |
@apollo/server npm | From 4.2.0 | 4.13.0 |
@apollo/server npm | From 5.0.0 | 5.4.0 |
@apollo/server npm | From 5.0.0 | 5.4.0 |
Products include Apollographql Apollo Server.
How do I fix CVE-2026-23897?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-23897 being exploited?
There is no known exploitation of CVE-2026-23897 in the wild and no public exploit code.
Sources
Also known as GHSA-mp6q-xf9x-fwf7, ROOT-APP-NPM-CVE-2026-23897.