Security readout for executives and security teams
Plain-English summary
CVE-2026-23519 affects RustCrypto’s cmov utility before 0.4.4 when compiled for thumbv6m-none-eabi Cortex-M0/M0+/M1 targets. A compiler output issue can make a supposedly constant-time operation non-constant-time, potentially leaking secrets through timing behavior. This is mainly urgent for embedded products using RustCrypto cryptography on those microcontrollers.
Executive priority
Treat as high priority for affected embedded cryptographic products, especially devices handling keys or sensitive data. For organizations not using RustCrypto cmov on thumbv6m-none-eabi microcontrollers, urgency is lower. Focus first on dependency inventory and firmware release planning.
Technical view
RustCrypto cmov promises conditional move intrinsics that remain constant-time. Before version 0.4.4, the portable cmovnz path on thumbv6m-none-eabi may compile into non-constant-time assembly. The assigned weakness is CWE-208, Observable Timing Discrepancy. CVSS v4.0 is 8.9, with high confidentiality impact and high attack complexity.
Likely exposure
Exposure is likely limited to projects using RustCrypto utils/cmov versions before 0.4.4 and building for thumbv6m-none-eabi, specifically Cortex-M0, M0+, or M1. General server, desktop, or unrelated embedded targets are not identified as affected in the provided sources.
Exploitation context
The issue is a timing side channel, not memory corruption or remote code execution. The CVSS vector lists network attack vector but high attack complexity. The source bundle does not report active exploitation, and KEV is false. Practical risk depends on reachable cryptographic operations and attacker ability to observe timing differences.
Researcher notes
The public record identifies the vulnerable condition and fix version, but does not include exploitation evidence. Review the linked commit and advisory to understand the code change. Avoid assuming broader platform impact beyond thumbv6m-none-eabi unless vendor sources expand the scope.
Mitigation direction
- Upgrade RustCrypto utils/cmov to version 0.4.4 or later.
- Prioritize embedded firmware builds targeting thumbv6m-none-eabi.
- Check RustCrypto’s advisory for any updated guidance.
- Rebuild and redeploy affected firmware after dependency update.
Validation and detection
- Inventory Rust projects using RustCrypto utils or cmov.
- Check dependency lockfiles for cmov versions below 0.4.4.
- Identify builds targeting thumbv6m-none-eabi Cortex-M0, M0+, or M1.
- Confirm rebuilt firmware uses cmov 0.4.4 or later.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-208: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-23519 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.9 (4.0)
- Known Exploited
- No
- Published
Vector: 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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
8.9HighVector: 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
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/RustCrypto/utils/security/advisories/GHSA-2gqc-6j2q-83qpCVE reference · x_refsource_CONFIRM
- https://github.com/RustCrypto/utils/commit/55977257e7c82a309d5e8abfdd380a774f0f9778CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Observable Timing Discrepancy
Observable Timing Discrepancy represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.