CVE-2026-26308
Last modified
CVE-2026-26308 is a high-severity vulnerability rated 8.2/10 on the CVSS scale. 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. EPSS estimates a 0.29% chance of exploitation in the next 30 days.
Description
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.
Metrics
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
Weakness Enumeration
Affected Software
| Vendor | Product | Versions |
|---|---|---|
| Envoyproxy | Envoy | < 1.34.13 |
| Envoyproxy | Envoy | >= 1.35.0, < 1.35.8 |
| Envoyproxy | Envoy | >= 1.36.0, < 1.36.5 |
| Envoyproxy | Envoy | 1.37.0 |
References
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-ghc4-35x6-crw5Exploit, Mitigation, Vendor Advisory
Timeline
- Published
- Last Modified
- Status
- Analyzed
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