CVE-2026-23519: rustcrypto cmov Observable Timing Discrepancy
Vulnerability summary
CVE-2026-23519 is a critical (CVSS 9.8) Observable Timing Discrepancy vulnerability in rustcrypto cmov. EPSS estimates a 0.56% chance of exploitation in the next 30 days, higher than 45.4% of scored vulnerabilities. 1 public exploit is recorded.
Advisory lineage
Upstream 0 · Downstream 0 · Related 3Timeline
- 15-01-2026PublishedVulnerability first disclosed.
- 15-01-2026Last modifiedVulnerability information updated.
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 metrics
6 scores · 5 sources · 2 versions- OSV · WolfiEcosystem advisory · calculated8.9HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
- OSV · ChainguardEcosystem advisory · calculated8.9HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
- OSV · Crates.ioEcosystem advisory · calculated8.9HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
- NVDNIST8.9HighCVSS: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:X/V:X/RE:X/U:X
EPSS trend
Probability
0.56%
Chance of exploitation in the next 30 days
Percentile
45%
Versus all other CVEs
30-day change
-0.01 pp
From 0.57% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundUtils
Maturity: poc
Weaknesses
CWE · root cause- CWE-208Observable Timing DiscrepancyTwo separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.
- CWE-203Observable DiscrepancyThe product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
Affected systems
Chainguard1 product
- yazi< 26.1.4-r2
Crates.Io1 product
- cmov< 0.4.4 | ≥ 0.0.0-0, < 0.4.4
Wolfi1 product
- yazi< 26.1.4-r2
4 vendors · 5 products
References
7 links- github.com/RustCrypto/utils/security/advisories/GHSA-2gqc-6j2q-83qpX Refsource CONFIRMAdvisoryWEBExploitVendor Advisory
- github.com/RustCrypto/utils/commit/55977257e7c82a309d5e8abfdd380a774f0f9778X Refsource MISCFIXWEBPatch
- github.com/RustCrypto/utilsPACKAGE
- crates.io/crates/cmovPACKAGE