Vulnerability Description
Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.18.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the router filter contains a null pointer dereference vulnerability when handling HTTP 303 (See Other) internal redirects for body-less non-GET/HEAD requests. When a POST, PUT, DELETE, or PATCH request without a body is sent to a route configured with internal redirect policy that includes 303 in redirect_response_codes, and the upstream responds with HTTP 303, the redirect handling code attempts to drain a request body buffer that was never allocated. This results in a segmentation fault that crashes the entire Envoy process. When route configured with internal_redirect_policy including 303 in redirect_response_codes and upstream must return HTTP 303 response, an unauthenticated attacker can exploit this to cause complete denial of service, terminating all active connections. This vulnerability is fixed in 1.35.13, 1.36.9, 1.37.5, and 1.38.3.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Envoyproxy | Envoy | >= 1.18.0, < 1.35.13 |
Related Weaknesses (CWE)
References
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjprExploitVendor Advisory
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-rcff-gw58-pjprExploitVendor Advisory
FAQ
What is CVE-2026-47221?
CVE-2026-47221 is a vulnerability with a CVSS score of 5.9 (MEDIUM). Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.18.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the router filter contains a null pointer dereference vuln...
How severe is CVE-2026-47221?
CVE-2026-47221 has been rated MEDIUM with a CVSS base score of 5.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-47221?
Check the references section above for vendor advisories and patch information. Affected products include: Envoyproxy Envoy.