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CVE-2026-26308

Envoyproxy Envoy broken access control

7.5 HIGHPublic exploitEPSS 0.36%
  1. Published10 Mar 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityHigh
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityHigh
IntegrityLow
AvailabilityNone
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

Affected products

Envoyproxy Envoy≥ 1.35.0 < 1.35.8 · ≥ 1.36.0 < 1.36.5 · < 1.34.13 · 1.37.0

Remediation

Fixed in
Envoyproxy Envoy≥ 1.35.8

References

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Frequently asked

Is CVE-2026-26308 being actively exploited?

CVE-2026-26308 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.36%.

How severe is CVE-2026-26308?

CVE-2026-26308 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.36% probability of exploitation.

Which products are affected by CVE-2026-26308?

Affected products include Envoyproxy Envoy.

How do I fix CVE-2026-26308?

Upgrade affected software to a fixed version, for example Envoyproxy Envoy 1.35.8 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-26308 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.