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CVE-2026-73552

Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values

CVSS 3.1 7.5 HIGHCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-73552

Published

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 HTTP RBAC accepts RFC-valid opaque header bytes but evaluates safe_regex values with RE2's UTF-8 subject semantics. A downstream client can preserve a prohibited marker and add an unrelated obs-text octet, causing RE2::FullMatch to return false and a negative RBAC policy to treat the invalid subject as an ordinary no-match. A byte-oriented route matcher can still observe the marker, allowing the request to reach a route intended to be denied. The relevant scope boundary is that plain positive ALLOW regexes normally fail closed, and exact, prefix, suffix, and contains matchers are not shown to have this subject-domain failure. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-73552

Published

envoy

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "envoyproxy",
                    "product": "envoy",
                    "versions": [
                        {
                            "version": "< 1.36.10",
                            "status": "affected"
                        },
                        {
                            "version": ">= 1.37.0, < 1.37.6",
                            "status": "affected"
                        },
                        {
                            "version": ">= 1.38.0, < 1.38.4",
                            "status": "affected"
                        },
                        {
                            "version": ">= 1.39.0, < 1.39.1",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON