CGI::Session::ID::md5 versions before 4.49 for Perl generate predictable session ids from low-entropy sources

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Summary

CVECVE-2026-56016
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-01 08:16:21 UTC
Updated2026-07-02 17:39:57 UTC
DescriptionCGI::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.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from ADP

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

EPSS: 0.003220000 probability, percentile 0.240950000 (date 2026-07-04)

Problem Types: CWE-338 | CWE-340 | CWE-340 CWE-340 Generation of Predictable Numbers or Identifiers | CWE-338 CWE-338 Use of Cryptographically Weak Pseudo-Random Number Generator

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA MARKSTOS CGISessionIDmd5 affected 4.49 custom Not specified

References

ReferenceSourceLinkTags
metacpan.org/release/MARKSTOS/CGI-Session-4.49/source/lib/CGI/Session/ID/m... 9b29abf9-4ab0-4765-b253-1875cd9b441e metacpan.org
metacpan.org/release/MARKSTOS/CGI-Session-4.49/changes 9b29abf9-4ab0-4765-b253-1875cd9b441e metacpan.org
www.openwall.com/lists/oss-security/2026/07/01/6 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Additional Advisory Data

SourceTimeEvent
CNA2026-06-30T00:00:00.000ZVersion 4.49 released with fix.

Solutions

CNA: Upgrade to CGI::Session 4.49 or later, which generates session ids from Crypt::SysRandom.

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