Information Exposure Through Timing Discrepancy in phpseclib - CVE-2026-40194
Published: April 10, 2026
Vulnerability identifier: #VU125780
CSH Severity: Low
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-40194
CWE-ID: CWE-208
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose limited security-sensitive information via a timing side channel.
The vulnerability exists due to observable timing discrepancy in SSH2::get_binary_packet() in phpseclib/Net/SSH2.php when verifying received SSH packet HMAC values. A remote attacker can send specially crafted SSH packets to disclose limited security-sensitive information via a timing side channel.
The vulnerable code path is reached for non-AEAD cipher and MAC combinations, while AEAD cipher modes use a different authentication path.
Affected software
phpseclib
Fedora
nextcloud
Fedora
nextcloud
How to mitigate CVE-2026-40194
Install security update from vendor's website.
phpseclib - addressed in versions 1.0.28, 2.0.53, 3.0.51
nextcloud - addressed in versions 33.0.3-1.el10_2, 33.0.3-1.el10_3, 33.0.3-1.fc42, 33.0.3-1.fc43, 33.0.3-1.fc44
nextcloud - addressed in versions 33.0.3-1.el10_2, 33.0.3-1.el10_3, 33.0.3-1.fc42, 33.0.3-1.fc43, 33.0.3-1.fc44