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CVE-2025-9231 Openssl Library CVE debrief

CVE-2025-9231 is a timing side-channel issue in OpenSSL’s SM2 signature implementation on 64-bit ARM platforms. According to the advisory and CVE description, timing measurements revealed a signal that could potentially enable remote recovery of the SM2 private key, although the reporter did not attempt a full network-based recovery. OpenSSL notes that this is not relevant to most TLS deployments because it does not directly support SM2 certificates in TLS, but the risk becomes more relevant in environments that add SM2 support through a custom provider. The issue is rated Moderate/Medium, and the FIPS modules for OpenSSL 3.5, 3.4, 3.3, 3.2, 3.1, and 3.0 are stated to be unaffected because SM2 is not an approved algorithm.

Vendor
Openssl Library
Product
Unknown
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2025-09-30
Original CVE updated
2026-05-11
Advisory published
2025-09-30
Advisory updated
2026-05-11

Who should care

Organizations using OpenSSL on 64-bit ARM systems where SM2 signatures are used, especially deployments that rely on custom providers or other non-default integrations that may expose SM2 private key operations remotely. Security teams responsible for cryptographic libraries, platform engineering, and any service operators who may have enabled SM2 outside standard TLS support should review this CVE.

Technical summary

The issue is a timing side-channel in SM2 signature computation on 64-bit ARM. The observed timing signal could, in principle, leak enough information to help recover the private key. OpenSSL says it does not directly support SM2 certificates in TLS, which limits exposure in standard deployments, but custom provider scenarios may make the issue reachable over a network. The FIPS modules mentioned in the advisory are not affected.

Defensive priority

Medium. The issue is not described as broadly exploitable in default TLS configurations, but it can matter in custom or specialized SM2 deployments on 64-bit ARM, where private key exposure would be high impact.

Recommended defensive actions

  • Review whether your OpenSSL usage on 64-bit ARM includes SM2 signing operations or custom providers that enable SM2 certificates.
  • Identify any services or applications that could expose SM2 private key operations remotely, including non-default TLS or provider-based integrations.
  • Apply the OpenSSL fix referenced by the official security advisory and linked commits in your build or package stream.
  • Verify whether your deployment depends on the affected non-FIPS OpenSSL code paths; the advisory states the listed FIPS modules are not affected.
  • Monitor vendor backports and distribution advisories for patched OpenSSL packages if you consume OpenSSL through an operating system or platform package manager.

Evidence notes

This debrief is based on the supplied CVE description, the NVD record, and the linked OpenSSL security advisory and GitHub commits. The CVE was published on 2025-09-30 and later modified on 2026-05-11. NVD metadata marks the vulnerability status as Deferred. The reporter observed a timing signal but did not attempt remote key recovery over a network. Claims about scope are limited to the supplied text: 64-bit ARM, SM2 signature computations, custom-provider TLS relevance, and FIPS modules not affected.

Official resources

Publicly disclosed on 2025-09-30 alongside the OpenSSL security advisory. The reporter noted a timing signal but did not attempt remote key recovery over a network. The record was later modified on 2026-05-11.