CVE-2026-47774
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.97%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.97% probability · 60th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-405, CWE-770, CWE-409
- Affected
- envoyproxy/envoy · redhat/openshift service mesh
- Source
- security-advisories@github.com
References
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8Mitigation, Vendor Advisory
- http://www.openwall.com/lists/oss-security/2026/06/04/15Mailing List, Mitigation, Third 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=2487465Exploit, Issue Tracking, Third Party Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47774.jsonThird Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.