Timing Side-Channel in Scalar Multiplication for Non-NIST EC Curves

Description

Issue summary: The generic elliptic-curve scalar multiplication used for ECDSA and SM2 signature operations with curves that do not have a dedicated implementation leaks information about the secret nonce through timing. Impact summary: An attacker able to measure signing times may learn information about the per-signature secret nonce, which over many signatures can, via a lattice / Hidden Number Problem attack, lead to recovery of the private key. CWE: CWE-208: Observable Timing Discrepancy Description: The generic elliptic-curve scalar multiplication used for curves that do not have a dedicated constant-time implementation pads the secret scalar with non-constant-time BIGNUM operations, so the time taken depends on the value of the secret scalar derived from the ECDSA and SM2 nonce. The leak is very small; observing it requires a large number of measurements. The effect is largest for curves whose group order lies on a machine-word boundary, such as brainpoolP384r1. Applications using ECDSA signing over the Brainpool and other generic prime curves, and SM2 signing on platforms that use the generic implementation, are vulnerable to this issue. The NIST curves P-256, P-384 and P-521 use dedicated constant-time implementations and are not affected. FIPS Impact: no The FIPS modules are not affected: the approved NIST curves used in the FIPS provider have dedicated constant-time implementations and do not use the affected code path.

Scores

EPSS (exploitation in 30 days)

0.44% · top 61% of all CVEs (5 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 3.7.

Weakness

• CWE-208 Observable Timing Discrepancy (opens in a new tab)All about CWE-208 and its CVEs

Affected products

• OpenSSL · OpenSSL

  • affected 4.0.0 – < 4.0.3
  • affected 3.6.0 – < 3.6.5
  • affected 3.5.0 – < 3.5.9
  • affected 3.4.0 – < 3.4.8
  • affected 3.0.0 – < 3.0.23
  • affected 1.1.1 – < 1.1.1zj
  • affected 1.0.2 – < 1.0.2zs

References (5)

• OpenSSL Advisory (opens in a new tab)vendor-advisory
• 4.0.3 git commit (opens in a new tab)patch
• 3.6.5 git commit (opens in a new tab)patch
• 3.5.9 git commit (opens in a new tab)patch
• 3.4.8 git commit (opens in a new tab)patch

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-54872](https://trackcve.app/badge/CVE-2026-54872.svg)](https://trackcve.app/cve/CVE-2026-54872)

Record last updated 29 Sept 2026, 17:28 UTC.