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CVE-2025-66442

18
FAUCET Score

CVE-2025-66442 identifies a compiler-induced timing side channel vulnerability affecting RSA and CBC/ECB decryption in Mbed TLS up to version 4.0.0 and TF-PSA-Crypto up to version 1.0.0, specifically when LLVM's select-optimize feature is utilized. With a CVSS score of 5.1 (Medium), this flaw requires local access and high attack complexity, but could result in a high impact on confidentiality by potentially allowing an attacker to extract sensitive cryptographic data. Currently, there is no indication of active exploitation, public exploit code, or significant community attention regarding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
<= 4.0.0CPE matchmatch criteria
cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*
<= 1.0.0CPE matchmatch criteria
cpe:2.3:a:arm:tf-psa-crypto:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.1MEDIUM

CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector
LOCAL
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
1.4
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.27%
Probability of exploitation in next 30 days
EPSS Percentile
19.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0027 is in the 9th percentile among its peer group of 1,595 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Advisories (1)

microsoft2026-Apr/CVE-2025-66442Moderate

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.

Apr 14, 2026

References

github.com / Mbed-TLS/mbedtls/releases
Release Notes
github.com / Mbed-TLS/TF-PSA-Crypto/releases
Release Notes
mbed-tls.readthedocs.io / en/latest/security-advisories
Vendor Advisory
mbed-tls.readthedocs.io / en/latest/security-advisories/mbedtls-security-advisory-2026-03-compiler-induced-constant-time-violations
Vendor Advisory