What’s Vulnerable › Vulnerabilities

CVE-2026-23519: RustCrypto cmov: thumbv6m-none-eabi compiler emits non-constant time assembly when using cmovnz

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-01-15 · updated 2026-06-17
• Weakness: CWE-208

Description

RustCrypto CMOV provides conditional move CPU intrinsics which are guaranteed on major platforms to execute in constant-time and not be rewritten as branches by the compiler. Prior to 0.4.4, the thumbv6m-none-eabi (Cortex M0, M0+ and M1) compiler emits non-constant time assembly when using cmovnz (portable version). This vulnerability is fixed in 0.4.4.

Affected products

• RustCrypto Cmov: before 0.4.4 — fixed in 0.4.4

How to fix

Upgrade to a fixed version: RustCrypto Cmov 0.4.4. Check the vendor advisory for mitigations.

References

• https://github.com/RustCrypto/utils/commit/55977257e7c82a309d5e8abfdd380a774f0f9778
• https://github.com/RustCrypto/utils/security/advisories/GHSA-2gqc-6j2q-83qp
• https://github.com/RustCrypto/utils/security/advisories/GHSA-2gqc-6j2q-83qp

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