CVE-2026-47774
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.
Executive briefing
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Evidence confidence: Not assessed Evidence-derived, not an exploitability verdict
Severity & attack characteristics
CVSS vector:Not supplied
No CVSS vector is currently available in the source record.
Technical explanation & impact
Technical root-cause details are not available in the current source record.
Assess the impact using the published CVSS metrics and the affected vendor component.
Affected products and versions
NVD has not supplied machine-readable vulnerable CPE product/version entries for this CVE. This is an information gap, not proof that no products are affected. Check the vendor advisory references below.
Remediation & validation
- Identify exposure by comparing the affected product and version ranges with your asset inventory, SBOM and externally exposed services.
- Review the linked vendor security advisory or patch notes. Upgrade to a vendor-confirmed fixed release; do not infer a fixed version from the CVE description.
- Until patched, consider restricting network access or disabling the affected feature where operationally safe. These are temporary controls, not a substitute for a vendor fix.
- Validate the remediation with a version check and vulnerability rescan, then retain change evidence.
No fixed version is displayed unless it is explicitly established by a vendor advisory. Follow the vendor's release notes for exact product and branch applicability.
Vendor advisories, patches & exploit references
No external references are currently supplied in the CVE record.