CVE-2026-73552Public exploitNetwork attack vectorHinoki check available

Authorization bypass via UTF-8 regex subject mismatch

Published Sep 21, 2026 · Updated Sep 21, 2026

Authorization bypass in affected Envoy releases allows remote attackers to reach routes protected by negative HTTP RBAC safe_regex rules. HeaderDataStringMatch passes RFC-valid opaque header bytes to RE2::FullMatch in UTF-8 mode, which collapses an invalid subject into an ordinary no-match. Exploitation requires accepted obs-text, negative regex logic, and a route that still recognizes the prohibited marker; impact is limited to resources reachable through that route.

CVSS severity7.5
High
EPSS probability0.47%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Authorization bypass in affected Envoy releases allows remote attackers to reach routes protected by negative HTTP RBAC safe_regex rules. HeaderDataStringMatch passes RFC-valid opaque header bytes to RE2::FullMatch in UTF-8 mode, which collapses an invalid subject into an ordinary no-match. Exploitation requires accepted obs-text, negative regex logic, and a route that still recognizes the prohibited marker; impact is limited to resources reachable through that route.

The record

CVE
CVE-2026-73552
Published
Sep 21, 2026
Updated
Sep 21, 2026
Vendor
Envoy Proxy
Product
Envoy
Classifications
CWE-863, CWE-20, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.36.10
  2. Affected versionversion=>= 1.37.0, < 1.37.6
  3. Affected versionversion=>= 1.38.0, < 1.38.4
  4. Affected versionversion=>= 1.39.0, < 1.39.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Envoy Proxy · Envoyversion=< 1.36.10; version=>= 1.37.0, < 1.37.6; version=>= 1.38.0, < 1.38.4; version=>= 1.39.0, < 1.39.1

Published CVSS scores

7.5Red Hat Product SecurityCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
7.5Envoy Proxy GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-863Incorrect Authorization
CWE-20Improper Input Validation
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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