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CVE-2026-34873

CRITICAL CVSS 3.1: 9.1 EPSS 0.04%
Updated Apr 07, 2026
Arm
Parameter Value
CVSS 9.1 (CRITICAL)
Affected Versions 3.5.0 — 4.1.0
Fixed In 3.6.6
Type CWE-287 (Improper Authentication)
Vendor Arm
Public PoC No

An issue was discovered in Mbed TLS 3.5.0 through 4.0.0. Client impersonation can occur while resuming a TLS 1.3 session.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption

CVSS Vector v3.1

Weakness Type (CWE)

CWE-287 Improper Authentication

Vulnerable Products 2

Configuration From (including) Up to (excluding)
Arm Mbed_Tls
cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
 3.5.0 3.6.6
Arm Mbed_Tls
cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
 4.0.0 4.1.0

References 2

https://mbed-tls.readthedocs.io/en/latest/security-advisories/
cve@mitre.org
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-…
cve@mitre.org
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