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CVE-2026-56016

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

5.9 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

0.51%Up 0.3 points since Jul 1, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.9

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

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.

Record
CVE-2026-56016
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-340, CWE-338
Updated
2026-11-02
EUVDEUVD-2026-40927 5.9

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.

Record
EUVD-2026-40927
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-r49c-4q8x-x33v 5.9

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

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.

Record
GHSA-r49c-4q8x-x33v
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-338
Updated
2026-11-02
NVD 5.9

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.

Record
CVE-2026-56016
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-338, CWE-340
Updated
2026-11-02
OSVALPINE-CVE-2026-56016 5.9

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.

Record
ALPINE-CVE-2026-56016
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVDEBIAN-CVE-2026-56016 5.9

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.

Record
DEBIAN-CVE-2026-56016
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2026-56016 5.9

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.

Record
UBUNTU-CVE-2026-56016
CVSS 3.1
5.9 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVMGASA-2026-0286 No score

Updated perl-CGI-Session package fixes a security vulnerability

The updated package fixes a security vulnerability: CGI::Session::ID::md5 versions before 4.49 for Perl generate predictable session ids from low-entropy sources. (CVE-2026-56016)

Record
MGASA-2026-0286
Updated
2026-11-02
OSVopenSUSE-SU-2026:11168-1 No score

perl-CGI-Session-4.490.0-1.1 on GA media

These are all security issues fixed in the perl-CGI-Session-4.490.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:11168-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
perl-cgi-session
Alpine:v3.24
before 4.49-r0
4.49-r0
libcgi-session-perl
Debian:12
All versions, plus listed versions
4.48-44.49-1
None known
libcgi-session-perl
Debian:13
All versions, plus listed versions
4.48-44.49-1
None known
libcgi-session-perl
Debian:14
before 4.49-1, plus listed versions
4.48-4
4.49-1
perl-CGI-Session
Mageia:10
before 4.490.0-1.mga10
4.490.0-1.mga10
libcgi-session-perl
Ubuntu:16.04:LTS
All versions, plus listed versions
4.48-24.48-3
None known
libcgi-session-perl
Ubuntu:18.04:LTS
All versions, plus listed versions
4.48-3
None known
libcgi-session-perl
Ubuntu:20.04:LTS
All versions, plus listed versions
4.48-3
None known
libcgi-session-perl
Ubuntu:22.04:LTS
All versions, plus listed versions
4.48-3
None known
libcgi-session-perl
Ubuntu:24.04:LTS
All versions, plus listed versions
4.48-4
None known
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Affected packages
PackageAffectedFixed
libcgi-session-perl
Ubuntu:25.10
All versions, plus listed versions
4.48-4build1
None known
libcgi-session-perl
Ubuntu:26.10
All versions, plus listed versions
4.48-4build14.49-1
None known
libcgi-session-perl
Ubuntu:26.04:LTS
All versions, plus listed versions
4.48-4build1
None known
perl-CGI-Session
openSUSE:Tumbleweed
before 4.490.0-1.1
4.490.0-1.1

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-56016 is a medium vulnerability (CVSS 5.9) in Markstos Cgi::session::id::md5, published July 1, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.51%, the 43rd percentile. Fixed in perl-cgi-session 4.49-r0.

References

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