CVE-2026-73064
Received Received - Intake

Mbed TLS TLS 1.3 Server Entropy Source Manipulation

Publication date: 2026-09-24

Last updated on: 2026-09-24

Assigner: MITRE

Description
In Mbed TLS 3.2.0 though 3.6.6 and 4.0.0 through 4.1.0, an attacker who can cause an entropy source to fail can remove or inject bytes into the start of the TLS stream. This only affects TLS 1.3 servers.

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Meta Information

Published
2026-09-24
Last Modified
2026-09-24
Generated
2026-09-24
AI Q&A
2026-09-24
EPSS Evaluated
N/A
NVD
CVE-2026-73064
EUVD
EUVD-2026-85930

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
mbed_tls mbedtls From 3.2.0 (inc) to 3.6.6 (inc)
mbed_tls mbedtls From 4.0.0 (inc) to 4.1.0 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-394 The product does not properly check when a function or operation returns a value that is legitimate for the function, but is not expected by the product.

Attack-Flow Graph

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Executive Summary

This vulnerability in Mbed TLS 3.2.0 through 3.6.6 and 4.0.0 through 4.1.0 allows an attacker who can cause an entropy source to fail to remove or inject bytes at the start of the TLS stream. This specifically impacts TLS 1.3 servers by potentially compromising the integrity of the encrypted communication.

Detection Guidance

Detecting this vulnerability requires checking the Mbed TLS version in use. Run 'mbedtls_version' or inspect the library files for version numbers between 3.2.0-3.6.6 or 4.0.0-4.1.0. Monitor TLS 1.3 server logs for entropy source failures or unexpected data at the start of TLS streams.

Impact Analysis

If you are using a vulnerable version of Mbed TLS as a TLS 1.3 server, an attacker could manipulate the start of your TLS stream. This could lead to data corruption, unauthorized access, or other security breaches depending on how the TLS stream is used in your system.

Compliance Impact

This vulnerability could compromise the integrity of encrypted data, potentially violating requirements for data integrity and confidentiality in standards like GDPR and HIPAA. Organizations using vulnerable versions may face compliance risks due to weakened cryptographic protections.

Mitigation Strategies

Upgrade Mbed TLS to a version outside the affected range (3.2.0-3.6.6 or 4.0.0-4.1.0). If upgrading is not possible, disable TLS 1.3 on affected servers or implement additional monitoring for entropy source failures.

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