CVE-2026-3256

Name: CVE-2026-3256
Creator: NVD / NIST
Published: 2026-03-28T19:16:56.57+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 0.53%

Last modified Jun 17, 2026

CVE-2026-3256 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. HTTP::Session versions through 0.53 for Perl defaults to using insecurely generated session ids. HTTP::Session defaults to using HTTP::Session::ID::SHA1 to generate session ids using a SHA-1 hash seeded with the built-in rand function, the high resolution epoch time, and the PID. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. EPSS estimates a 0.53% chance of exploitation in the next 30 days.

Description

HTTP::Session versions through 0.53 for Perl defaults to using insecurely generated session ids. HTTP::Session defaults to using HTTP::Session::ID::SHA1 to generate session ids using a SHA-1 hash seeded with the built-in rand function, the high resolution epoch time, and the PID. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage. The distribution includes HTTP::session::ID::MD5 which contains a similar flaw, but uses the MD5 hash instead.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

0.53%

40.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions	Update
Ktat	Http\	<= 0.53	Session

References

https://metacpan.org/release/KTAT/http-session-0.53/source/lib/HTTP/Session/ID/MD5.pmProduct
https://metacpan.org/release/KTAT/http-session-0.53/source/lib/HTTP/Session/ID/SHA1.pmProduct
https://security.metacpan.org/docs/guides/random-data-for-security.htmlThird Party Advisory
http://www.openwall.com/lists/oss-security/2026/03/28/5Mailing List, Third Party Advisory

Timeline

Published: Mar 28, 2026
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2026-3256?

How severe is CVE-2026-3256?

CVE-2026-3256 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.53% probability of exploitation in the next 30 days.

How do I fix CVE-2026-3256?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-3256?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST