CVE-2026-54872 Timing Side-Channel in Scalar Multiplication for Non-NIST EC Curves
Attackers can recover private keys from ECDSA/SM2 signatures on non-NIST curves via timing side-channels in OpenSSL's generic scalar multiplication.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54872?
CVE-2026-54872 is a low-severity vulnerability in Openssl Openssl, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-208
Which versions are affected by CVE-2026-54872?
It affects 1 product.
Products include Openssl Openssl.
How do I fix CVE-2026-54872?
Apply the vendor's patch.
Is CVE-2026-54872 being exploited?
There is no known exploitation of CVE-2026-54872 in the wild and no public exploit code.
Other vulnerabilities in Openssl Openssl
Sources
Also known as ALPINE-CVE-2026-54872, AZL-105360, AZL-105450, AZL-105480, AZL-105504, AZL-105573 and 11 more.