Medium severity · published Apr 1, 2026
CVE-2025-66442
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature
5.1
CVSS
0.3%
EPSS
No
On KEV
Description
In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.
CVSS vector
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Local
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 19% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MT
Mbed Tls · Arm
through 4.0.0 · source: NVD
TF
Tf-psa-crypto · Arm
through 1.0.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66442
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66442
Release Notes
https://github.com/Mbed-TLS/TF-PSA-Crypto/releases
Release Notes
https://github.com/Mbed-TLS/mbedtls/releases
Vendor Advisory
https://mbed-tls.readthedocs.io/en/latest/security-advisories/
Vendor Advisory
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-compiler-induced-constant-time-violations/
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