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

CVE-2026-26311 has a CVSS 3.1 base score of 5.9 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.0%.

Which versions of Envoy are affected by CVE-2026-26311?

Organizations using Envoy should be aware of moderate risk from CVE-2026-26311, a use-after-free vulnerability rated CVSS 5.9. Exploitation could compromise the security of affected deployments.

Is there a public PoC exploit available for CVE-2026-26311?

Yes, a public proof-of-concept exploit is available for CVE-2026-26311. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-26311?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

Envoy CVE-2026-26311

MEDIUM

Use After Free (CWE-416)

2026-03-10 security-advisories@github.com

GHSA-84xm-r438-86px

Use After Free Envoy Envoyproxy

5.9

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

5.9 MEDIUM

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

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:55 vuln.today

PoC Detected

Mar 11, 2026 - 16:03 vuln.today

Public exploit code

CVE Published

Mar 10, 2026 - 20:16 nvd

MEDIUM 5.9

DescriptionGitHub Advisory

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.

AnalysisAI

Envoy proxy versions before 1.37.1, 1.36.5, 1.35.8, and 1.34.13 contain a use-after-free vulnerability in the HTTP connection manager that allows attackers to trigger denial of service by sending data frames on streams after they have been reset. Public exploit code exists for this vulnerability, and no patch is currently available. The flaw enables filter callbacks to execute on logically cleaned-up streams, potentially causing service disruption or state corruption.

Technical ContextAI

Classified as CWE-416 (Use After Free). Affects Envoy. 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::decodeDa