CVE-2026-26311: Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, a logic vulnerability in Envoy's HTTP connection ...

Description

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, a logic vulnerability in Envoy's HTTP connection manager (FilterManager) that allows for Zombie Stream Filter Execution. This issue creates a "Use-After-Free" (UAF) or state-corruption window where filter callbacks are invoked on an HTTP stream that has already been logically reset and cleaned up. The vulnerability resides in source/common/http/filter_manager.cc within the FilterManager::decodeData method. The ActiveStream object remains valid in memory during the deferred deletion window. If a DATA frame arrives on this stream immediately after the reset (e.g., in the same packet processing cycle), the HTTP/2 codec invokes ActiveStream::decodeData, which cascades to FilterManager::decodeData. FilterManager::decodeData fails to check the saw_downstream_reset_ flag. It iterates over the decoder_filters_ list and invokes decodeData() on filters that have already received onDestroy(). This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.

Metrics

CVSS 3.1

5.9/10

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

EPSS Probability

0.34%

25.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-416

Affected Software

Vendor	Product	Versions
Envoyproxy	Envoy	< 1.34.13
Envoyproxy	Envoy	>= 1.35.0, < 1.35.8
Envoyproxy	Envoy	>= 1.36.0, < 1.36.5
Envoyproxy	Envoy	1.37.0

References

https://github.com/envoyproxy/envoy/security/advisories/GHSA-84xm-r438-86pxExploit, Mitigation, Vendor Advisory

Timeline

Published: Mar 10, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-26311?

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, a logic vulnerability in Envoy's HTTP connection manager (FilterManager) that allows for Zombie Stream Filter Execution. This issue creates a "Use-After-Free" (UAF) or state-corruption window where filter callbacks are invoked on an HTTP stream that has already been logically reset and cleaned up. The vulnerability resides in source/common/http/filter_manager.cc within the FilterManager::decodeData method. The ActiveStream object remains valid in memory during the deferred deletion window. If a DATA frame arrives on this stream immediately after the reset (e.g., in the same packet processing cycle), the HTTP/2 codec invokes ActiveStream::decodeData, which cascades to FilterManager::decodeData. FilterManager::decodeData fails to check the saw_downstream_reset_ flag. It iterates over the decoder_filters_ list and invokes decodeData() on filters that have already received onDestroy(). This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.

How severe is CVE-2026-26311?

CVE-2026-26311 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.

How do I fix CVE-2026-26311?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.