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Vulnerability record · CVE-2026-47774 · published 17 June 2026

CVE-2026-47774: Envoyproxy envoy allocation without limits vulnerability

Envoyproxy · Envoy

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.

7.5 CVSS 3.1 High EPSS 1.1% · top 37.1% CWE-405 · CWE-405CWE-770 · Allocation without limits
7.5CVSS 3.1 base score
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
10References, 1 tagged exploit
20 Jul 2026Last modified by NVD

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/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8 MitigationVendor Advisory
http://www.openwall.com/lists/oss-security/2026/06/04/15 Mailing ListMitigationThird Party Advisory
https://access.redhat.com/errata/RHSA-2026:26210 Third Party Advisory
https://access.redhat.com/errata/RHSA-2026:26222 Third Party Advisory
https://access.redhat.com/errata/RHSA-2026:26231 Third Party Advisory
https://access.redhat.com/errata/RHSA-2026:26247 Third Party Advisory
https://access.redhat.com/errata/RHSA-2026:27114 Third Party Advisory
https://access.redhat.com/security/cve/CVE-2026-47774 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2487465 ExploitIssue TrackingThird Party Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47774.json Third Party Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-47774), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.