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CVE-2025-40926

31
FAUCET Score

CVE-2025-40926 is a critical vulnerability affecting Plack::Middleware::Session::Simple versions through 0.04 for Perl, where insecure session ID generation allows for predictable session IDs. The default generator uses a cryptographically weak combination of rand, epoch time, and PID, making session IDs guessable. This vulnerability carries a CVSS score of 9.8 (Critical) due to its network-based attack vector, low attack complexity, and high impact on confidentiality, integrity, and availability. While there is no known active exploitation, public exploit code, or KEV listing, the vulnerability has garnered some community discussion and media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.05CPE matchmatch criteria
cpe:2.3:a:kazeburo:plack\:\:middleware\:\:session\:\:simple:*:*:*:*:*:perl:*:*
>= 0, < 0.05CPE match
cpe:2.3:a:kazeburo:plack\:\:middleware\:\:session\:\:simple:*:*:*:*:*:perl:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.43%
Probability of exploitation in next 30 days
EPSS Percentile
35.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0043 is in the 12th percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / kazeburo/Plack-Middleware-Session-Simple/commit/760bb358b8f53e52cf415888a4ac858fd99bb24e.patch
Patch
github.com / kazeburo/Plack-Middleware-Session-Simple/pull/4
Issue TrackingPatch
metacpan.org / release/KAZEBURO/Plack-Middleware-Session-Simple-0.04/source/lib/Plack/Middleware/Session/Simple.pm
Issue TrackingProduct
metacpan.org / release/KAZEBURO/Plack-Middleware-Session-Simple-0.05/changes
security.metacpan.org / docs/guides/random-data-for-security.html
Third Party Advisory
cve.org / CVERecord
Third Party Advisory