Secret disclosure via optimizer-inserted conditional branch
Published Jan 15, 2026 · Updated Jan 15, 2026
Observable timing discrepancy in RustCrypto cmov before 0.4.4 allows remote attackers to infer secrets through ARM32 side channels. In portable cmovnz, LLVM recognizes bitnz as Boolean and rewrites the unprotected wrapping subtraction into a conditional branch. Exploitation requires code built for an affected 32-bit ARM target to use this path with secret-dependent data; the bounded impact is disclosure through microarchitectural timing, not data modification or service interruption.
Summary
What happened
Observable timing discrepancy in RustCrypto cmov before 0.4.4 allows remote attackers to infer secrets through ARM32 side channels. In portable cmovnz, LLVM recognizes bitnz as Boolean and rewrites the unprotected wrapping subtraction into a conditional branch. Exploitation requires code built for an affected 32-bit ARM target to use this path with secret-dependent data; the bounded impact is disclosure through microarchitectural timing, not data modification or service interruption.
The record
- CVE
- CVE-2026-23519
- Published
- Jan 15, 2026
- Updated
- Jan 15, 2026
- Vendor
- RustCrypto
- Product
- cmov
- Classifications
- CWE-208, CWE-203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 15, 2026CVE publishedPublication date reported by the CVE source.
- Jan 15, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 0.4.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- GHSA-2gqc-6j2q-83qp cmovnz reproducerproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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