# CVE-2026-73552: Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values

> CVE-2026-73552: Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values. CVSS 7.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-73552
Last updated: 2026-10-05T14:35:24Z

- Published: 2026-09-21 19:37 UTC · Updated: 2026-10-05 14:35 UTC · Assigner: GitHub\_M
- CVSS: 7.5 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- EPSS: 0.49%, 42th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-20

## 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 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.

## Affected vendors and products

- envoyproxy: envoy

## Tracked companies

- [Google Cloud](https://rewindex.com/company/google-cloud.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-73552)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-73552)
- [https://github.com/envoyproxy/envoy/commit/5650cb9770d4420ec2bcbed8b90be06f564ecc07](https://github.com/envoyproxy/envoy/commit/5650cb9770d4420ec2bcbed8b90be06f564ecc07)
- [https://github.com/envoyproxy/envoy/commit/7d1dee5dda66434d84437cc5c85153aa03955e26](https://github.com/envoyproxy/envoy/commit/7d1dee5dda66434d84437cc5c85153aa03955e26)
- [https://github.com/envoyproxy/envoy/commit/c2b9a19dc081f03be6a9b4ca932673e5e7a33d18](https://github.com/envoyproxy/envoy/commit/c2b9a19dc081f03be6a9b4ca932673e5e7a33d18)
- [https://github.com/envoyproxy/envoy/commit/f3726765f3a12ddc76dcb52c0b79bec3d95ced1c](https://github.com/envoyproxy/envoy/commit/f3726765f3a12ddc76dcb52c0b79bec3d95ced1c)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.36.10](https://github.com/envoyproxy/envoy/releases/tag/v1.36.10)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.37.6](https://github.com/envoyproxy/envoy/releases/tag/v1.37.6)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.38.4](https://github.com/envoyproxy/envoy/releases/tag/v1.38.4)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.39.1](https://github.com/envoyproxy/envoy/releases/tag/v1.39.1)
- [https://github.com/envoyproxy/envoy/security/advisories/GHSA-23xh-2qxr-3xv8](https://github.com/envoyproxy/envoy/security/advisories/GHSA-23xh-2qxr-3xv8)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-73552 · Markdown: https://rewindex.com/cve/CVE-2026-73552.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-73552 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:09:43.190Z