What is CVE-2025-59438?

CVE-2025-59438 is a medium-severity vulnerability in Arm Mbed TLS, classified under CWE-208. CVSS score: 5.3/10. Published 2025-10-21.

How severe is CVE-2025-59438?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Arm Mbed TLS

CVE-2025-59438

Mbed TLS through 3.6.4 has an Observable Timing Discrepancy.

Published 2025-10-21 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.003 (16.4th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 16.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.000

Affected products

Arm Mbed TLS

Weakness classification (CWE)

CWE-208

References

mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/ (Vendor Advisory)
mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory… (Vendor Advisory)

Frequently asked questions

What is CVE-2025-59438?: CVE-2025-59438 is a medium-severity vulnerability in Arm Mbed TLS, classified under CWE-208. CVSS score: 5.3/10. Published 2025-10-21.
How severe is CVE-2025-59438?: Medium severity. CVSS v3 base score is 5.3 out of 10.