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CVE-2026-23519: Rustcrypto Cmov Security Vulnerability (CVSS 8.9)

CVE-2026-23519 is a high severity security vulnerability in Rustcrypto Cmov with a CVSS score of 8.9. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Last updated: Jun 17, 2026

Quick answer

Direct answer

CVE-2026-23519 is a high severity security vulnerability in Rustcrypto Cmov with a CVSS score of 8.9. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Risk scores

CVSS base score
8.9HIGH
EPSS probability
0.56%
Higher than 45 percent of all CVEs
CISA KEV
Not listed
CVSS metricWhat it means
Attack vector (AV:N)Network: reachable remotely
Attack complexity (AC:H)High complexity
Attack requirements (AT:N)No attack requirements
Privileges required (PR:N)No privileges required
User interaction (UI:N)No user interaction
Confidentiality (VC:H)High confidentiality impact
Integrity (VI:N)No integrity impact
Availability (VA:N)No availability impact

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:X/V:X/RE:X/U:X

About Rustcrypto Cmov

CVE-2026-23519 affects Rustcrypto Cmov, a product from Rustcrypto. Before acting, confirm where Rustcrypto Cmov runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.

What the flaw is

In plain terms: 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.

Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Affected versions and timeline

FieldDetail
ProductRustcrypto Cmov
Affected versionsCmov before 0.4.4
PublishedJan 15, 2026
Last modifiedJun 17, 2026
Added to CISA KEVNot listed
Assigning CNAsecurity-advisories@github.com

How to detect it

  • Inventory every instance of Rustcrypto Cmov and record the running version against the affected range above.
  • Check external attack surface scans for internet facing instances of the component.
  • Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
  • Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.

How to fix it

  • Apply the fixed version of Rustcrypto Cmov named in the vendor advisory.
  • If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
  • Rescan after the change to prove the exposure is gone, then close the ticket.

CTEM action plan

CTEM stageWhat to do for this CVE
ScopeAdd every business service that depends on Rustcrypto Cmov to the current CTEM cycle.
DiscoverFind all instances, including shadow and cloud deployments, and record versions and exposure.
PrioritizeRank using EPSS and CVSS together with asset exposure and business impact.
ValidateConfirm the flaw is reachable and exploitable in your environment and that compensating controls work.
MobilizeAssign the fix to the asset owner with a due date matched to the priority, then verify closure.

CWE References

Technical References

Frequently asked questions

CVE-2026-23519 is a high severity security vulnerability in Rustcrypto Cmov with a CVSS score of 8.9. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

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