CVE-2025-66442: arm mbed_tls Covert Timing Channel
CVSS: 5.1v3.1MediumAnalyzed
AliasesUBUNTU-CVE-2025-66442DEBIAN-CVE-2025-66442
Published 01-04-2026Last modified 01-04-2026
Vulnerability summary
CVE-2025-66442 is a medium (CVSS 5.1) Covert Timing Channel vulnerability in arm mbed_tls. EPSS estimates a 0.27% chance of exploitation in the next 30 days, higher than 18% of scored vulnerabilities.
CVSS score
5.1/10
010
Medium · v3.1 (CVE.org)EPSS score
0.27%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 01-04-2026PublishedVulnerability first disclosed.
- 01-04-2026Last modifiedVulnerability information updated.
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 metrics
4 scores · 4 sources · 1 versionMedium 5.1Preferred score · CVE.org (CNA)
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:NSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated5.1MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- OSV · DebianEcosystem advisory · calculated5.1MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- NVDNIST5.1MediumCVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS trend
Probability
0.27%
Chance of exploitation in the next 30 days
Percentile
18%
Versus all other CVEs
30-day change
0.00 pp
From 0.27% on 19-09-2026
19-09-202619-10-2026
EPSS score0.27%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Arm2 products
- mbed_tls≤ 4.0.0
- tf-psa-crypto≤ 1.0.0
Debian1 product
- mbedtlsAll versions (No fix recorded)
Ubuntu1 product
- mbedtlsAll versions (No fix recorded)
3 vendors · 4 products
