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%.

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

View

Vulnerability Assessment

Weakness	CWE CWE-416 OWASP Top 10:2025 A06:2021 - Vulnerable and Outdated Components ASVS 5.0 V15 - Secure Coding and Architecture Memory lifecycle management MITRE ATT&CK 2 techniques across 2 tactics: Execution, Privilege Escalation The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. Sign in to read
Impact	CVSS 5.9 (MEDIUM). Attack vector: Network. Complexity: High. Privileges required: None. User interaction: None. Public exploit/POC available.
Exploit ScenarioDerived	An attacker could exploit this vulnerability to compromise the affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

No patch listed yet 0.0% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAIv1 – Mar 12, 2026

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.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 21:55 CVSS 5.9

RemediationAI

Fixed in version 1.37.1. Restrict network access to the affected service where possible.

Affected Packages

go github.com/envoyproxy/envoy no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in go

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

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

Know when Envoy gets its next vulnerability

Watch products and get an email when something new is published
Check this CVE against your own stack and servers
Exploit and PoC references, threat intelligence from 22 sources

Continue with Google Continue with GitHub

No credit card · 7-day full trial

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

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.

Executive ViewAI

Why It Matters

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. Proof-of-concept code is publicly available. Organizations should apply vendor updates when available and monitor for exploitation.

Business Impact: Low

Compensating Controls

Apply vendor patch. If patching is delayed: enable ASLR/DEP, apply network segmentation.

Threat Intelligence Overview

EPSS Score

0.0%

Top 99% exploitable

Exploit

POC

Public exploit code exists

Data Quality

5 sources

Confidence: Medium

NVD

CVE.org

EPSS

GitHub

VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC Yes

EPSS 0.0%

Patch available No

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Human Impact

Low

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +30

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Use After Free HIGH

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Affected Products (CPE)GitHub Advisory

cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*

cpe:2.3:a:envoyproxy:envoy:1.37.0:*:*:*:*:*:*:*

Related Vulnerabilities in Envoy Proxy Multiple Vulnerabilities

View all 5

CVE-2026-26330 MEDIUM

5.3

CVE-2026-26310 MEDIUM POC

5.9

CVE-2026-26309 MEDIUM POC

5.3

CVE-2026-26308 HIGH POC

7.5

More in Envoy

View all

CVE-2023-44487 HIGH Act Now POC

7.5 Oct 10

Denial of service against HTTP/2 server implementations allows remote unauthenticated attackers to exhaust server resour

CVE-2026-111497 CRITICAL Act Now POC

9.2 Oct 21

Remote code execution is possible in Node.js releases that bundle a vulnerable Brotli decoder: a malformed brotli-compre

CVE-2023-27488 CRITICAL Act Now POC

9.8 Apr 04

Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.8

CVE-2019-18802 CRITICAL Act Now POC

9.8 Dec 13

An issue was discovered in Envoy 1.12.0. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable,

CVE-2019-18801 CRITICAL Act Now POC

9.8 Dec 13

An issue was discovered in Envoy 1.12.0. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable,

CVE-2023-27493 CRITICAL Act Now POC

9.1 Apr 04

Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.1

CVE-2023-27491 CRITICAL Act Now POC

9.1 Apr 04

Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.1

CVE-2023-27487 CRITICAL Act Now POC

9.1 Apr 04

Envoy is an open source edge and service proxy designed for cloud-native applications. Rated critical severity (CVSS 9.1

CVE-2020-25017 HIGH This Week POC

8.3 Oct 01

Envoy through 1.15.0 only considers the first value when multiple header values are present for some HTTP headers. Rated

CVE-2019-9900 HIGH This Week POC

8.3 Apr 25

When parsing HTTP/1.x header values, Envoy 1.9.0 and before does not reject embedded zero characters (NUL, ASCII 0x0). R

CVE-2024-53270 HIGH This Week POC

7.5 Dec 18

Envoy is a cloud-native high-performance edge/middle/service proxy. Rated high severity (CVSS 7.5), this vulnerability i

Same weakness CWE-416 – Use After Free

View all

CVE-2019-0708 CRITICAL POC

9.8

CVE-2015-5119 CRITICAL POC

9.8

CVE-2014-0322 HIGH POC

8.8

CVE-2012-4792 HIGH POC

8.8

CVE-2009-4324 HIGH POC

7.8

CVE-2015-0313 CRITICAL POC

9.8

CVE-2015-5122 CRITICAL POC

9.8

CVE-2013-2551 HIGH POC

8.8

Same technique Use After Free

View all

CVE-2012-4969 HIGH POC

8.1

References

Advisories & patches

ADVISORY https://vuldb.com/?id.350164

Search Externally

GitHub PoC

Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC

Back