What is the CVSS score of CVE-2025-66442?

CVE-2025-66442 has a CVSS 3.1 base score of 5.1 (Medium). CVSS vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N. EPSS exploitation probability: 0.0%.

N A CVE-2025-66442

EUVD-2025-209171 MEDIUM

Covert Timing Channel (CWE-385)

2026-04-01 mitre

Information Disclosure Red Hat N A

5.1

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

5.1 MEDIUM

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

Red Hat

5.9 MEDIUM

qualitative

Primary rating from NVD.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Lifecycle Timeline

EUVD ID Assigned

Apr 01, 2026 - 19:45 euvd

EUVD-2025-209171

Analysis Generated

Apr 01, 2026 - 19:45 vuln.today

CVE Published

Apr 01, 2026 - 00:00 nvd

MEDIUM 5.1

DescriptionCVE.org

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.

AnalysisAI

Compiler-induced timing side channel in Mbed TLS through 4.0.0 and TF-PSA-Crypto through 1.0.0 allows information disclosure of RSA private keys and CBC/ECB-decrypted plaintext when LLVM's select-optimize feature is enabled during compilation. The vulnerability arises from compiler optimization that violates constant-time implementation guarantees, potentially exposing cryptographic material to timing analysis attacks despite developers' explicit use of constant-time code patterns.

Technical ContextAI

Mbed TLS and TF-PSA-Crypto are widely-used cryptographic libraries that implement RSA and symmetric encryption (CBC, ECB modes). The vulnerability involves a compiler-specific issue where LLVM's select-optimize optimization pass transforms conditional logic in constant-time RSA and block cipher decryption routines into data-dependent timing variations. The root cause falls under timing side-channel weakness (CWE-208, Information Disclosure via Timing Attack) - the libraries contain correctly-written constant-time implementations, but the compiler optimization defeats these protections. This affects any application compiled with LLVM select-optimize enabled, including embedded systems, TLS implementations, and cryptographic services relying on these libraries for secure key material protection.

RemediationAI

Upgrade Mbed TLS to a patched version released after 4.0.0 and upgrade TF-PSA-Crypto to a patched version released after 1.0.0. Consult the official release pages (https://github.com/Mbed-TLS/mbedtls/releases and https://github.com/Mbed-TLS/TF-PSA-Crypto/releases) for exact patched version numbers. As an interim mitigation, disable LLVM's select-optimize feature during compilation by avoiding aggressive optimization flags or explicitly disabling select-optimize in build configurations. For applications where recompilation is impractical, review whether select-optimize is actually enabled in the current build (it is not enabled by default); if not, the system is unaffected. Verify patched versions have been released by checking the Mbed TLS security advisory at https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-compiler-induced-constant-time-violations/.