CVE-2026-3256: HTTP::Session versions before 0.54 for Perl defaults to using insecurely generated session ids. HTTP::Session

Q: How do I fix CVE-2026-3256?

http\: upgrade to newer than 0.53. Exact commands for each OS are on this page.

Q: Is CVE-2026-3256 being exploited?

CVE-2026-3256 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-3256 affect?

CVE-2026-3256 affects http\. Severity is critical (CVSS 9.8). HTTP::Session versions before 0.54 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

Q: How urgent is CVE-2026-3256?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-3256 is a critical-severity flaw (CVSS 9.8) affecting http\. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

HTTP::Session versions before 0.54 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

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Weakness	CWE-338, CWE-340
Published	2026-03-28
Last modified	2026-06-29

Publisher (CNA): CPANSec · Vendor: ktat

Last updated 2026-06-29 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-28 19:16 UTCPublished CVE record published
2026-06-29 07:16 UTCUpdated Record last modified

ktat http\ UPGRADE

Affected: <= 0.53

Fixed in: newer than 0.53

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy http || rpm -q http || http --version

2. UPGRADE to newer than 0.53 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade http

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade http

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-3256?

http\: upgrade to newer than 0.53. Exact commands for each OS are on this page.

Is CVE-2026-3256 being exploited?

CVE-2026-3256 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-3256 affect?

CVE-2026-3256 affects http\. Severity is critical (CVSS 9.8). HTTP::Session versions before 0.54 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

How urgent is CVE-2026-3256?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Perl vulnerabilities

References

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