Apollo Router Core: Browser Bug Enables Bypass of XS-Search Prevention via Read-Only Cross-Site Request Forgery

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.3 · CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

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, the 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 Router 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 Router's docs for more details on CORS, CSRF attacks, and Apollo Router'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…

Published by the source

26 Mar 2026, 22:09 UTC

Last modified by the source

26 Mar 2026, 22:09 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-hff2-gcpx-8f4p

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# Patch Next advisory brief: GHSA-hff2-gcpx-8f4p

Advisory: Apollo Router Core: Browser Bug Enables Bypass of XS-Search Prevention via Read-Only Cross-Site Request Forgery
IDs: GHSA-hff2-gcpx-8f4p
Record: https://patchnext.com/advisories/ghsa-hff2-gcpx-8f4p (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: apollo-router 2.12.1, 2.10.2, 1.61.13. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io apollo-router: affected >= 2.11.0, < 2.12.1; >= 2.0.0, < 2.10.2; < 1.61.13; fixed in 2.10.2, 1.61.13, 2.12.1

## Suggested inspection (read-only)
- crates.io apollo-router: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on apollo-router.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hff2-gcpx-8f4p (GitHub-reviewed advisory GHSA-hff2-gcpx-8f4p lists affected ranges: crates.io apollo-router >=2.11.0 =2.0.0 =0 <1.61.13)

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