CVE-2026-56016
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 29% of all known CVEs.
References
Related Vulnerabilities
Other CWE-338 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2008-0166 | High | 7.5 | 71% | - | Fix |
| CVE-2009-2367 | Critical | 9.8 | 23% | - | - |
| CVE-2024-29868 | Critical | 9.1 | 6.0% | - | - |
| CVE-2024-31497 | Medium | 5.9 | 5.8% | - | Fix |
| CVE-2021-43799 | High | 8.6 | 5.4% | - | Fix |
| CVE-2008-3280 | Medium | 5.9 | 4.0% | - | - |
Common questions
How do I fix CVE-2026-56016?
Upgrade libcgi-session-perl on debian unstable to 4.49-1 or later.
Is CVE-2026-56016 being actively exploited?
Not that we know of. CVE-2026-56016 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.36% is the estimated probability that it will be exploited in the next 30 days. That is higher than 29% of all scored CVEs.
How severe is CVE-2026-56016?
CVE-2026-56016 has a CVSS v3 base score of 5.9, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-56016 affect?
Published advisories record a fix for libcgi-session-perl (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-02.