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3.7

OpenSSL signing may expose private keys through timing

CVE-2026-54872 · published 20 days ago
Summary

The generic signing routine in OpenSSL (including the Debian, Canonical and Node.js builds) leaks tiny timing differences when using certain non‑standard curves such as Brainpool. An attacker who can record many signatures could piece together enough information to recover the private key. Switch to the built‑in NIST curves or upgrade to a version of OpenSSL that uses constant‑time code for all curves.

What to do
  • Update canonical openssl to version 3.0.2-0ubuntu1.30.
  • Update canonical openssl to version 3.0.13-0ubuntu3.16.
  • Update canonical openssl to version 3.5.5-1ubuntu3.6.
  • Update alpine openssl to version 3.3.7-r2.
  • Update canonical openssl to version 1.0.1f-1ubuntu2.27+esm17.
  • Update canonical openssl to version 1.0.2g-1ubuntu4.20+esm19.
  • Update canonical openssl to version 1.1.1-1ubuntu2.1~18.04.23+esm11.
  • Update canonical openssl1.0 to version 1.0.2n-1ubuntu5.13+esm7.
  • Update canonical openssl to version 1.1.1f-1ubuntu2.24+esm6.
  • Update debian openssl to version 3.5.7-1~deb13u3.
  • Update debian openssl to version 3.6.5-1.
  • Update openssl to version 3.3.7-r2.
  • Update bellsoft openssl to version 3.0.22-r1.
  • Update bellsoft openssl to version 3.5.9-r0.
  • Update openssl to version 3.0.22-r1.
  • Update openssl to version 3.5.9-r0.
Affected software
Ecosystem VendorProductAffected versions
– openssl openssl < 4.0.3
>= 1.0.2, < 1.0.2zs
>= 1.1.1, < 1.1.1zj
>= 3.0.0, < 3.0.23
>= 3.4.0, < 3.4.8
>= 3.5.0, < 3.5.9
>= 3.6.0, < 3.6.5
>= 4.0.0, < 4.0.3
Debian:12 debian openssl All versions
Ubuntu:Pro:14.04:LTS canonical openssl < 1.0.1f-1ubuntu2.27+esm17
Fix: upgrade to 1.0.1f-1ubuntu2.27+esm17
Ubuntu:Pro:16.04:LTS canonical edk2 All versions
Ubuntu:Pro:16.04:LTS canonical nodejs All versions
Ubuntu:Pro:18.04:LTS canonical openssl1.0 < 1.0.2n-1ubuntu5.13+esm7
Fix: upgrade to 1.0.2n-1ubuntu5.13+esm7
Ubuntu:22.04:LTS canonical openssl < 3.0.2-0ubuntu1.30
Fix: upgrade to 3.0.2-0ubuntu1.30
Ubuntu:Pro:FIPS-preview:22.04:LTS canonical openssl-fips All versions
Ubuntu:24.04:LTS canonical openssl < 3.0.13-0ubuntu3.16
Fix: upgrade to 3.0.13-0ubuntu3.16
Ubuntu:26.04:LTS canonical edk2-hwe All versions
Ubuntu:26.04:LTS canonical openssl < 3.5.5-1ubuntu3.6
Fix: upgrade to 3.5.5-1ubuntu3.6
Alpine:v3.21 alpine openssl < 3.3.7-r2
Fix: upgrade to 3.3.7-r2
Ubuntu:Pro:16.04:LTS canonical openssl < 1.0.2g-1ubuntu4.20+esm19
Fix: upgrade to 1.0.2g-1ubuntu4.20+esm19
Ubuntu:Pro:18.04:LTS canonical openssl < 1.1.1-1ubuntu2.1~18.04.23+esm11
Fix: upgrade to 1.1.1-1ubuntu2.1~18.04.23+esm11
Ubuntu:Pro:20.04:LTS canonical openssl < 1.1.1f-1ubuntu2.24+esm6
Fix: upgrade to 1.1.1f-1ubuntu2.24+esm6
Debian:13 debian openssl < 3.5.7-1~deb13u3
Fix: upgrade to 3.5.7-1~deb13u3
Debian:14 debian openssl < 3.6.5-1
Fix: upgrade to 3.6.5-1
Alpine:v3.21 – openssl >= 1.0.2, < 3.3.7-r2
Fix: upgrade to 3.3.7-r2
Alpaquita:23 bellsoft openssl >= 3.0.8-r4, < 3.0.22-r1
Fix: upgrade to 3.0.22-r1
Alpaquita:25 bellsoft openssl >= 3.5.0-r0, < 3.5.9-r0
Fix: upgrade to 3.5.9-r0
Alpaquita:stream bellsoft openssl >= 3.1.1-r1, < 3.5.9-r0
Fix: upgrade to 3.5.9-r0
BellSoft Hardened Containers:23 – openssl >= 3.0.8-r4, < 3.0.22-r1
Fix: upgrade to 3.0.22-r1
BellSoft Hardened Containers:25 – openssl >= 3.5.0-r0, < 3.5.9-r0
Fix: upgrade to 3.5.9-r0
BellSoft Hardened Containers:stream – openssl >= 3.1.1-r1, < 3.5.9-r0
Fix: upgrade to 3.5.9-r0
Original advisory text
Timing Side-Channel in Scalar Multiplication for Non-NIST EC Curves
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.
References
Fix within
Internet-facing 60 days
Internal At next upgrade
  • Not known to be exploited
  • Needs hands-on effort to exploit
  • Gives an attacker partial control
Severity
3.7 Low
Exploitation
<1% chance of attack within 30 days
Type
CWE-208Observable Timing Discrepancy
Timeline
Published29 Sep 2026
Updated19 Oct 2026
First seen29 Sep 2026
Sources
CVE-2026-54872 · NVD
CVE-2026-54872 · MITRE
DEBIAN-CVE-2026-54872 · OSV
UBUNTU-CVE-2026-54872 · OSV
CVE-2026-54872 · OSV
ALPINE-CVE-2026-54872 · OSV
BELL-CVE-2026-54872 · OSV
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