How severe is CVE-2026-3256?

CVE-2026-3256 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-3256 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (41st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-3256?

CVE-2026-3256 affects Ktat Http. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-3256?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-3256 have an EU (EUVD) identifier?

Yes. CVE-2026-3256 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16939.

When was CVE-2026-3256 published?

CVE-2026-3256 was published on 2026-03-28 and last updated on 2026-06-29.

CVE-2026-3256

CVE-2026-3256 is a critical-severity vulnerability in Ktat Http with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-338.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 1% (41st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-16939
Weakness: CWE-338
Affected product: Ktat Http
Published: 2026-03-28
Last modified: 2026-06-29

Description

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 for cryptographic usage. The distribution includes HTTP::session::ID::MD5 which contains a similar flaw, but uses the MD5 hash instead.

Frequently asked questions

What is CVE-2026-3256?: 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 for cryptographic usage. The distribution includes HTTP::session::ID::MD5 which contains a similar flaw, but uses the MD5 hash instead.
How severe is CVE-2026-3256?: CVE-2026-3256 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-3256 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (41st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-3256?: CVE-2026-3256 affects Ktat Http. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-3256?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-3256 have an EU (EUVD) identifier?: Yes. CVE-2026-3256 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16939.
When was CVE-2026-3256 published?: CVE-2026-3256 was published on 2026-03-28 and last updated on 2026-06-29.

References

Affected products (1)

cpe:2.3:a:ktat:http\:\:session:*:*:*:*:*:perl:*:*

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