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Vulnerability record · CVE-2026-23519 · published 15 January 2026

CVE-2026-23519: Rustcrypto cmov observable discrepancy vulnerability

Rustcrypto · Cmov

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.

8.9 CVSS 4.0 High EPSS 0.57% · top 55.3% CWE-208 · CWE-208CWE-203 · Observable discrepancy
8.9CVSS 4.0 base score
0.57%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

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

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

2.0CVE-2026-50185Rustcrypto cmov vulnerabilityRustCrypto CMOV provides conditional move CPU intrinsics which are guaranteed on major platforms to execute in constant-time and not be rewritten as …EPSS 0.16%

Source: NIST National Vulnerability Database (record CVE-2026-23519), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.