CVE-2026-26308
RBAC Bypass via HTTP Header Concatenation in Envoy Proxy
Publication date: 2026-03-10
Last updated on: 2026-03-11
Assigner: GitHub, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| envoyproxy | envoy | to 1.34.13 (exc) |
| envoyproxy | envoy | From 1.35.0 (inc) to 1.35.8 (exc) |
| envoyproxy | envoy | From 1.36.0 (inc) to 1.36.5 (exc) |
| envoyproxy | envoy | 1.37.0 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-863 | The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the Envoy RBAC (Role-Based Access Control) filter prior to versions 1.37.1, 1.36.5, 1.35.8, and 1.34.13. The issue is in how Envoy validates HTTP headers when multiple values are present for the same header name. Instead of checking each header value individually, Envoy concatenates all values into a single comma-separated string. This allows attackers to bypass RBAC policies, especially "Deny" rules, by sending duplicate headers that obscure the malicious value from exact-match checks.
How can this vulnerability impact me? :
This vulnerability can allow attackers to bypass security policies enforced by Envoy's RBAC filter. Specifically, attackers can circumvent "Deny" rules by exploiting the way Envoy processes multiple header values, potentially gaining unauthorized access or performing actions that should be blocked. This can lead to compromised confidentiality and integrity of the system.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, you should upgrade Envoy to one of the fixed versions: 1.37.1, 1.36.5, 1.35.8, or 1.34.13.