Is CVE-2026-26311 actively exploited?

No active exploitation of CVE-2026-26311 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-26311 be exploited remotely?

Yes. CVE-2026-26311 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-26311?

CVE-2026-26311 has a CVSS score of 5.9 (MEDIUM).

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MEDIUM

CVE-2026-26311

CWE-416Published: March 10, 2026· Updated: Mar 11, 2026

5.9

CVSS v3.1

EPSS:0.01%probability of exploitation in 30 daysPercentile:1.4th

Official 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.

NVD Source

Technical Analysis

CVE-2026-26311 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 5.9.

From a weakness classification perspective (CWE-416): Use-after-free vulnerabilities involve accessing memory after it has been freed, often enabling arbitrary code execution.