CVE-2025-40931
Predictable MD5-based session IDs allow web session hijacking.
Is CVE-2025-40931 being exploited?
Not confirmed. CVE-2025-40931 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.58% probability of exploitation in the next 30 days.
How severe is CVE-2025-40931?
CVE-2025-40931 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2025-40931?
Yes. A fix has been recorded for CVE-2025-40931. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-40931 affect?
CVE-2025-40931 affects Perl apps using Apache::Session::Generate::MD5. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2025-40931?
Patch upgrade to fixed version with secure RNG
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Attacker can predict session IDs to hijack web sessions and impersonate users.
Immediate action required
- affected<= 1.94
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.