What’s Vulnerable › Vulnerabilities

CVE-2025-47917

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-07-20 · updated 2026-06-17
• Weakness: CWE-416

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).

Affected products

• mbedtls: before 3.6.4 — fixed in 3.6.4

How to fix

Upgrade to a fixed version: mbedtls 3.6.4. Check the vendor advisory for mitigations.

References

• https://github.com/Mbed-TLS/mbedtls-docs/blob/main/security-advisories/mbedtls-security-advisory-2025-06-7.md
• https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/
• https://lists.debian.org/debian-lts-announce/2025/08/msg00013.html
• https://lists.debian.org/debian-lts-announce/2025/08/msg00025.html

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