CVE-2026-73552
Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values
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.
INFO
Published Date :
Sept. 21, 2026, 8:17 p.m.
Last Modified :
Sept. 21, 2026, 8:17 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update Envoy to version 1.36.10 or later.
- Update Envoy to version 1.37.6 or later.
- Update Envoy to version 1.38.4 or later.
- Update Envoy to version 1.39.1 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-73552.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-73552 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-73552
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-73552 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-73552 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by [email protected]
Sep. 21, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Added CWE CWE-20 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/73xxx/CVE-2026-73552.json">CVE-2026-73552</a> Added Reference https://github.com/envoyproxy/envoy/commit/5650cb9770d4420ec2bcbed8b90be06f564ecc07 Added Reference https://github.com/envoyproxy/envoy/commit/7d1dee5dda66434d84437cc5c85153aa03955e26 Added Reference https://github.com/envoyproxy/envoy/commit/c2b9a19dc081f03be6a9b4ca932673e5e7a33d18 Added Reference https://github.com/envoyproxy/envoy/commit/f3726765f3a12ddc76dcb52c0b79bec3d95ced1c Added Reference https://github.com/envoyproxy/envoy/releases/tag/v1.36.10 Added Reference https://github.com/envoyproxy/envoy/releases/tag/v1.37.6 Added Reference https://github.com/envoyproxy/envoy/releases/tag/v1.38.4 Added Reference https://github.com/envoyproxy/envoy/releases/tag/v1.39.1 Added Reference https://github.com/envoyproxy/envoy/security/advisories/GHSA-23xh-2qxr-3xv8