Vulnerability Description
Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service. The issue arises from the combination of two behaviors. First, cookie header bytes are not fully accounted for during request header size validation in Envoy. Second, HPACK header block limits in oghttp2/quiche are enforced on encoded bytes without a corresponding limit on total decoded header size. Together, these behaviors allow a malicious client to cause large decoded header allocations while bypassing the intended request header size protections. Versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1 contain a fix. No complete workaround is known short of applying a fix. Possible temporary mitigations include disabling downstream HTTP/2 where operationally feasible; enforcing stricter request header and cookie limits before traffic reaches Envoy; and monitoring Envoy memory usage for abnormal growth under HTTP/2 traffic.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Envoyproxy | Envoy | < 1.35.11 |
| Redhat | Openshift Service Mesh | >= 2.6, < 2.6.17 |
Related Weaknesses (CWE)
References
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8MitigationVendor Advisory
- http://www.openwall.com/lists/oss-security/2026/06/04/15Mailing ListMitigationThird Party Advisory
- https://access.redhat.com/errata/RHSA-2026:26210Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:26222Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:26231Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:26247Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:27114Third Party Advisory
- https://access.redhat.com/security/cve/CVE-2026-47774Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2487465ExploitIssue TrackingThird Party Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47774.jsonThird Party Advisory
FAQ
What is CVE-2026-47774?
CVE-2026-47774 is a vulnerability with a CVSS score of 7.5 (HIGH). Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.35.11, 1.36.7, 1.37.3, and 1.38.1, a vulnerability in Envoy's HTTP/2 downstream request proce...
How severe is CVE-2026-47774?
CVE-2026-47774 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-47774?
Check the references section above for vendor advisories and patch information. Affected products include: Envoyproxy Envoy, Redhat Openshift Service Mesh.