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CVE-2026-73551

5.3 · MEDIUM

Envoy is an open source edge and service proxy designed for cloud-native applications.

Published Sep 21, 2026envoyproxyCWE-647EPSS 0.53%

Overview

CVE-2026-73551 is a medium-severity vulnerability affecting envoyproxy envoy. It was published on September 21, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy's URL normalization does not recognize dot and dotdot path segments when they carry semicolon parameters. A request such as /user/..;foo=bar/admin is therefore not canonicalized to /admin even when path normalization is enabled. If an upstream interprets the segment according to RFC 3986 while Envoy applies routing or RBAC to the uncollapsed path, a remote client can cause path confusion and bypass path-based security policy. The relevant scope boundary is that the security consequence depends on a downstream/upstream path interpretation mismatch or a path-based Envoy decision. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Remediation

Check the references section for vendor advisories and patches from envoyproxy. Update envoy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected products

VendorProductVersionsStatus
envoyproxyenvoy>= 0, < 1.36.10Affected

References

GitHubgithub.com/envoyproxy/envoy/commit/28b6d60a6d96edeece121cac5be701eb46cc7f24GitHubgithub.com/envoyproxy/envoy/commit/d40a68b0a30a003c4e0a9fd3af637f828b52c37bGitHubgithub.com/envoyproxy/envoy/commit/e9d6c329f9a3ff19432bf39b60c601df7e3eda33GitHubgithub.com/envoyproxy/envoy/commit/f74d1107c4f5c9679b66f7a03a6c5b75ddde1989GitHubgithub.com/envoyproxy/envoy/releases/tag/v1.36.10GitHubgithub.com/envoyproxy/envoy/releases/tag/v1.37.6GitHubgithub.com/envoyproxy/envoy/releases/tag/v1.38.4GitHubgithub.com/envoyproxy/envoy/releases/tag/v1.39.1GitHubgithub.com/envoyproxy/envoy/security/advisories/GHSA-2w8w-rfw7-8gg4

How CyberStrike helps

Frequently asked questions

What is CVE-2026-73551?

CVE-2026-73551 is a medium-severity vulnerability affecting envoyproxy envoy. It was published on September 21, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-73551?

This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-73551?

Check the references section for vendor advisories and patches from envoyproxy. Update envoy to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-73551?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-73551 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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