CVE-2026-73552 Envoy: HTTP RBAC safe_regex can fail open on RFC-valid obs-text header values
Attackers can bypass HTTP RBAC restrictions in Envoy by crafting headers with specific bytes that cause regex matchers to fail open, allowing access to denied routes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73552?
CVE-2026-73552 is a high-severity authentication bypass vulnerability in Envoyproxy Envoy, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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 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.
Weakness: CWE-20
Which versions are affected by CVE-2026-73552?
1 open source package ship an affected version, including envoy. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
envoy Bitnami | All versions | 1.36.10, 1.37.6, 1.38.4, 1.39.1 |
Products include Envoyproxy Envoy.
How do I fix CVE-2026-73552?
Upgrade envoy to a fixed version for your release line: 1.36.10, 1.37.6, 1.38.4 or 1.39.1.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-73552 being exploited?
There is no known exploitation of CVE-2026-73552 in the wild and no public exploit code.
Other vulnerabilities in Envoyproxy Envoy
Sources
Also known as BIT-envoy-2026-73552, GHSA-23xh-2qxr-3xv8, MINI-2v24-rcx9-g5mh, MINI-3vfc-25jf-f449, MINI-gfwq-5jpm-m3jf, MINI-whvg-vwww-5f8h.