CVE-2026-26308

7.5 HIGH 0.3% exploit odds Fix listed Auth & access Browser & mail

What it is

Envoy is a high-performance edge/middle/service proxy. Prior to 1.37.1, 1.36.5, 1.35.8, and 1.34.13, the Envoy RBAC (Role-Based Access Control) filter contains a logic vulnerability in how it validates HTTP headers when multiple values are present for the same header name. Instead of validating each header value individually, Envoy concatenates all values into a single comma-separated string. This behavior allows attackers to bypass RBAC policies—specifically "Deny" rules—by sending duplicate headers, effectively obscuring the malicious value from exact-match mechanisms. This vulnerability is fixed in 1.37.1, 1.36.5, 1.35.8, and 1.34.13.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure.
Exploit odds: 0.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-03-10 20:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 10:26 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.3% in the next 30 days (EPSS).
Severity: 7.5 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-03-10 20:16 UTC
Last modified: 2026-06-17 10:26 UTC
Exploit probability: 0.3% · EPSS, next 30 days
Weakness: CWE-863 · Incorrect authorization
Record status: Analyzed

Affected

Envoyproxy Envoy < 1.34.13
Envoyproxy Envoy < 1.35.8
Envoyproxy Envoy < 1.36.5
Envoyproxy Envoy 1.37.0

Attack profile CVSS 3.1 · 7.5

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: Low
Availability: None

Raw vector

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

Is it in your code?

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Read https://cve-list.com/agent/cve/CVE-2026-26308.md and follow it. Check whether this project is affected by CVE-2026-26308. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record