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

Medium · published April 1, 2026

CVSS v3.1
5.1
EPSS
0%
Percentile
18.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.1 · MEDIUM
Vector
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00270 · 18.2th percentile
Published
2026-04-01T00:00Z
EPSS history
Timeline
  • 01 APR 00:00Z
    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
    cvelistv5