CVE-2025-47917

Publication date 20 July 2025

Last updated 25 March 2026

Ubuntu priority

Cvss 3 Severity Score

Description

Mbed TLS before 3.6.4 allows a use-after-free in certain situations of applications that are developed in accordance with the documentation. The function mbedtls_x509_string_to_names() takes a head argument that is documented as an output argument. The documentation does not suggest that the function will free that pointer; however, the function does call mbedtls_asn1_free_named_data_list() on that argument, which performs a deep free(). As a result, application code that uses this function (relying only on documented behavior) is likely to still hold pointers to the memory blocks that were freed, resulting in a high risk of use-after-free or double-free. In particular, the two sample programs x509/cert_write and x509/cert_req are affected (use-after-free if the san string contains more than one DN).

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
mbedtls	25.10 questing	Vulnerable
	25.04 plucky	Ignored end of life, was needed
	24.04 LTS noble	Fixed 2.28.8-1ubuntu0.1~esm1
	22.04 LTS jammy	Fixed 2.28.0-1ubuntu0.1~esm1
	20.04 LTS focal	Fixed 2.16.4-1ubuntu2+esm1
	18.04 LTS bionic	Fixed 2.8.0-1ubuntu0.1~esm1
	16.04 LTS xenial	Vulnerable

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Notes

hlibk

The fix for the issue introduced a runtime error issue and a memory leak issue, which were fixed in subsequent commits (listed in the patches).

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
mbedtls	Upstream: 19d2c91 Upstream: acdcb7f Upstream: 4dd52b7 Upstream: 0803df2 Upstream: f9ac5e7

Severity score breakdown

Parameter	Value
Base score	8.9 · High
Attack vector	Network
Attack complexity	High
Privileges required	None
User interaction	None
Scope	Changed
Confidentiality	Low
Integrity impact	High
Availability impact	High
Vector	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:H

References

Related Ubuntu Security Notices (USN)

USN-8123-1
Mbed TLS vulnerabilities
25 March 2026