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CVE-2026-47774 envoyproxy CVE debrief

CVE-2026-47774 is a high-severity vulnerability in Envoy's HTTP/2 downstream request processing. An unauthenticated remote client can trigger excessive memory consumption, potentially resulting in OOM termination of the Envoy process and denial of service. This issue arises from a combination of two behaviors: incomplete accounting of cookie header bytes during request header size validation and HPACK header block limits enforced on encoded bytes without a corresponding limit on total decoded header size. Affected versions include those prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1. Users should update to a patched version to mitigate this vulnerability.

Vendor
envoyproxy
Product
envoy
CVSS
HIGH 7.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-17
Original CVE updated
2026-07-20
Advisory published
2026-06-17
Advisory updated
2026-07-20

Who should care

Users of Envoy, particularly those using versions prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, should be aware of this vulnerability and take steps to mitigate it. This includes updating to a patched version and potentially implementing temporary mitigations such as disabling downstream HTTP/2 or enforcing stricter request header and cookie limits.

Technical summary

The vulnerability in Envoy's HTTP/2 downstream request processing allows an unauthenticated remote client to trigger excessive memory consumption. This is due to incomplete accounting of cookie header bytes during request header size validation and HPACK header block limits enforced on encoded bytes without a corresponding limit on total decoded header size. The affected versions are prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1. Patched versions include 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

Defensive priority

High

Recommended defensive actions

  • Update to Envoy version 1.35.11, 1.36.7, 1.37.3, or 1.38.1, or later
  • Disable downstream HTTP/2 where operationally feasible
  • Enforce stricter request header and cookie limits before traffic reaches Envoy
  • Monitor Envoy memory usage for abnormal growth under HTTP/2 traffic
  • Consider implementing additional security measures to detect and prevent potential attacks

Evidence notes

The information provided is based on the CVE-2026-47774 record and related sources. The vulnerability is confirmed to exist in Envoy versions prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1. The patched versions are confirmed to fix the issue.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-47774 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-47774

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-47774 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-47774

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.