Information Exposure Through Timing Discrepancy in phpseclib - #VU145995
Published: August 27, 2026
Vulnerability identifier: #VU145995
CSH Severity: Low
CVSS v4: 7.2 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-208
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to recover a private key.
The vulnerability exists due to observable timing discrepancy in the pure-PHP X25519 scalar multiplication implementation when performing scalar multiplication operations. A local user can observe per-ladder-step timing or libgmp call counts to recover a private key.
Exploitation requires a reused or long-lived X25519 private key, knowledge of the victim\'s public key, and execution of the pure-PHP path with per-ladder-step observation capability.
Affected software
phpseclib
Remediation
Install security update from vendor's website.
phpseclib - addressed in versions 3.0.57, 4.0.1