What is CVE-2026-23519?

CVE-2026-23519 is a critical-severity vulnerability in Rustcrypto Cmov, classified under CWE-208. CVSS score: 9.8/10. Published 2026-01-15.

How severe is CVE-2026-23519?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Rustcrypto Cmov

CVE-2026-23519

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.

Published 2026-01-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.006 (44.8th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.006 · change: +0.000

Affected products

Rustcrypto Cmov
Rustcrypto Utils — versions < 0.4.4

Weakness classification (CWE)

References

github.com/RustCrypto/utils/security/advisories/GHSA-2gqc-6j2q-83qp (Exploit, Vendor Advisory)
github.com/RustCrypto/utils/commit/55977257e7c82a309d5e8abfdd380a774f0f9778 (Patch)

Frequently asked questions

What is CVE-2026-23519?: CVE-2026-23519 is a critical-severity vulnerability in Rustcrypto Cmov, classified under CWE-208. CVSS score: 9.8/10. Published 2026-01-15.
How severe is CVE-2026-23519?: Critical severity. CVSS v3 base score is 9.8 out of 10.