Information Exposure Through Timing Discrepancy in OpenSSL - CVE-2026-77696
Published: September 30, 2026
Vulnerability identifier: #VU152963
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-77696
CWE-ID: CWE-208
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to recover a private key.
The vulnerability exists due to an observable timing discrepancy in SM2 signature generation when performing arithmetic on secret nonce and private-key values. A remote attacker can measure signing times across many signatures to recover a private key.
The issue affects SM2 signature generation on all platforms.
Affected software
OpenSSL
Debian Linux
openssl (Debian package)
Debian Linux
openssl (Debian package)
How to mitigate CVE-2026-77696
Install security update from vendor's website.
OpenSSL - addressed in versions 1.0.2zs, 1.1.1zj, 3.0.23, 3.4.8, 3.5.9, 3.6.5, 4.0.3
openssl (Debian package) - update to 3.5.7-1~deb13u3
openssl (Debian package) - update to 3.5.7-1~deb13u3