CVE-2026-56016 CGI::Session::ID::md5 versions before 4.49 for Perl generate predictable session ids from low-entropy sources
Attackers can predict session IDs due to low-entropy generation, allowing them to impersonate users and bypass authentication in Perl applications.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-56016?
CVE-2026-56016 is a medium-severity vulnerability in MARKSTOS CGI::Session::ID::md5, published on 1 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
CGI::Session::ID::md5 versions before 4.49 for Perl generate predictable session ids from low-entropy sources.
The generate_id method builds the session id from a MD5 digest of the process id, the epoch time, and the built-in rand() function. All three are predictable, low-entropy sources: the PID is drawn from a small range, the epoch time can be guessed or read from the HTTP Date header, and Perl's rand() is unsuitable for security purposes because it is predictable and reversible.
An attacker who predicts a session id can impersonate the corresponding session and bypass authentication.
Which versions are affected by CVE-2026-56016?
Linux distribution packages (1)
perl-CGI-Session openSUSE:Tumbleweed | All versions | 4.490.0-1.1 |
How do I fix CVE-2026-56016?
Upgrade to a fixed version.
Is CVE-2026-56016 being exploited?
There is no known exploitation of CVE-2026-56016 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-56016, DEBIAN-CVE-2026-56016, GHSA-r49c-4q8x-x33v, MGASA-2026-0286, UBUNTU-CVE-2026-56016, openSUSE-SU-2026:11168-1.