EnvoyProxy Envoy up to 1.36.9/1.37.5/1.38.3/1.39.0 URL Normalization access control

Summaryinfo

A vulnerability, which was classified as problematic, has been found in EnvoyProxy Envoy up to 1.36.9/1.37.5/1.38.3/1.39.0. Affected by this issue is some unknown functionality of the component URL Normalization. Performing a manipulation results in access control. This vulnerability is known as CVE-2026-73551. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in EnvoyProxy Envoy up to 1.36.9/1.37.5/1.38.3/1.39.0. It has been classified as problematic. This affects an unknown functionality of the component URL Normalization. The manipulation with an unknown input leads to a access control vulnerability. CWE is classifying the issue as CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. This is going to have an impact on confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-73551 since 08/12/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1068 according to MITRE ATT&CK.

Upgrading to version 1.36.10, 1.37.6, 1.38.4 or 1.39.1 eliminates this vulnerability.

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Productinfo

Type

• Firewall Software

Vendor

• EnvoyProxy

Name

• Envoy

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28
• 1.29
• 1.30
• 1.31
• 1.32
• 1.33
• 1.34
• 1.35
• 1.36
• 1.36.0
• 1.36.1
• 1.36.2
• 1.36.3
• 1.36.4
• 1.36.5
• 1.36.6
• 1.36.7
• 1.36.8
• 1.36.9
• 1.37
• 1.37.0
• 1.37.1
• 1.37.2
• 1.37.3
• 1.37.4
• 1.37.5
• 1.38
• 1.38.0
• 1.38.1
• 1.38.2
• 1.38.3
• 1.39.0

License

• free

Website

• Product: https://github.com/envoyproxy/envoy/

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