CVE-2026-47774: Envoyproxy Envoy denial of service (CVSS 7.5)

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 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Envoyproxy Envoy≥ 1.36.0 < 1.36.7 · ≥ 1.37.0 < 1.37.3 · < 1.35.11 · 1.38.0

Redhat Openshift Service Mesh≥ 2.6 < 2.6.17 · ≥ 3.0 < 3.0.12 · ≥ 3.1 < 3.1.9 · ≥ 3.2 < 3.2.6

Remediation

Fixed in

Envoyproxy Envoy≥ 1.36.7

Redhat Openshift Service Mesh≥ 2.6.17

Patch & vendor advisories

https://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8

References

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://github.com/envoyproxy/envoy/security/advisories/GHSA-22m2-hvr2-xqc8MitigationVendor Advisory
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47774.jsonThird Party Advisory
http://www.openwall.com/lists/oss-security/2026/06/04/15Mailing ListMitigationThird Party Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-47774 being actively exploited?

CVE-2026-47774 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 1.05%.

How severe is CVE-2026-47774?

CVE-2026-47774 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 1.05% probability of exploitation.

Which products are affected by CVE-2026-47774?

Affected products include Envoyproxy Envoy, Redhat Openshift Service Mesh.

How do I fix CVE-2026-47774?

Upgrade affected software to a fixed version, for example Envoyproxy Envoy 1.36.7, Redhat Openshift Service Mesh 2.6.17 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-47774 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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