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Vulnerability · Published Sep 21, 2026 · Assigned by GitHub_M

CVE-2026-73551Envoy: Path normalization does not handle dot and dotdot segments with parameters

Medium 5.3

In plain English

A medium-severity security flaw in envoy from envoyproxy. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities).

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.5%top 55.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
envoyproxy envoy < 1.36.10>= 1.37.0, < 1.37.6>= 1.38.0, < 1.38.4>= 1.39.0, < 1.39.1

Weakness: CWE-647 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

References