CVE-2026-73552

7.5 HIGHpublic exploit available

Published 2026-09-21 · Updated 2026-09-21

AI risk analysis

Summary: The flaw allows a downstream client to bypass RBAC policies by manipulating opaque headers, potentially allowing unauthorized access to routes intended for denial.
Exploitability: Exploitation requires control over HTTP requests and knowledge of specific header manipulations; preconditions include the use of affected Envoy versions prior to 1.36.10, 1.37.6, 1.38.4, or 1.39.1.
Blast radius: If exploited, this could lead to unauthorized access and potential data exposure in cloud-native applications relying on RBAC for security.
Prioritized remediation: Upgrade Envoy to version 1.36.10, 1.37.6, 1.38.4, or 1.39.1 immediately to mitigate the risk.

rbac-bypassheader-manipulationcloud-nativesecurity-update

Analysis generated locally by qwen2.5:7b-instruct (no data left the box). AI-assisted — verify against primary sources before acting.

NVD 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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Weaknesses

CWE-20

Public exploit & PoC references

All references

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

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