CVE-2026-34873
Analyzed Analyzed - Analysis Complete
Client Impersonation in Mbed TLS 3.5.0–4.0.0 TLS 1.3 Resume

Publication date: 2026-04-01

Last updated on: 2026-06-05

Assigner: MITRE

Description
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.
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Meta Information
Published
2026-04-01
Last Modified
2026-06-05
Generated
2026-06-16
AI Q&A
2026-04-02
EPSS Evaluated
2026-06-15
NVD
CVE-2026-34873
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
trustedfirmware mbed_tls From 4.0.0 (inc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-287 When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
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Impact Analysis

An attacker could impersonate a client when resuming a TLS 1.3 session, potentially allowing unauthorized access or interception of communications that are expected to be secure.

Compliance Impact

The provided information does not specify how the client impersonation vulnerability in Mbed TLS affects compliance with common standards and regulations such as GDPR or HIPAA.

Mitigation Strategies

To mitigate the client impersonation vulnerability in Mbed TLS during TLS 1.3 session resumption, you should update Mbed TLS to a fixed version where this issue is resolved.

The advisory mentions available work-arounds and fix commits, so applying the latest security patches or upgrading to a version beyond 4.0.0 that addresses this vulnerability is recommended.

Executive Summary

This vulnerability exists in Mbed TLS versions 3.5.0 through 4.0.0 and involves client impersonation during the resumption of a TLS 1.3 session.

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