Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2026-3256 is a critical-severity PRNG (CWE-338) vulnerability in Ktat Http\. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Forge Web Credentials (T1606); ranked at the 42th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SC-12 (Cryptographic Key Establishment and Management) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-3256 affects the Perl module HTTP::Session in versions through 0.53, which defaults to insecure session ID generation. The module uses HTTP::Session::ID::SHA1, seeding a SHA-1 hash with Perl's built-in rand function, high-resolution epoch time, and the process ID (PID). These inputs are predictable: PIDs draw from a small range, epoch time can be guessed or leaked via the HTTP Date header, and rand is unsuitable for cryptography. A similar issue exists in the included HTTP::Session::ID::MD5, which uses MD5 instead of SHA-1. This flaw corresponds to CWE-338 (use of cryptographically weak PRNG) and CWE-340 (generation of predictable numbers or identifiers), earning a CVSS v3.1 base score of 9.8.
Remote attackers require no privileges, authentication, or user interaction to exploit this over the network with low complexity. By predicting session IDs due to the weak entropy sources, adversaries can hijack active sessions, impersonate legitimate users, or perform session fixation attacks, potentially leading to high confidentiality, integrity, and availability impacts as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
Advisories reference the vulnerable source code in HTTP::Session 0.53 and a Metacpan security guide emphasizing proper random data generation for security-sensitive uses in Perl. The Openwall oss-security mailing list announcement from March 28, 2026, details the issue, recommending avoidance of the default ID generators in favor of cryptographically secure alternatives.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16939
Vulnerability Data
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.…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 9 hardening rules · 4 OS baselines
V7.2.3V11.5.1V11.3.4
Mitigating Controls (NIST 800-53 r5) AI
Requiring specific approved cryptography for protection directly mandates use of strong PRNGs instead of weak ones.
Developer testing and evaluation can discover predictable number generation through targeted analysis or fuzzing of identifier creation routines.
Cryptographic key establishment and management mandates proper entropy and randomness during generation, directly stopping predictable identifiers at the source.
Authenticator management requires secure initial distribution and handling of authenticators, structurally preventing predictable values from being usable.
Engineering principles applied during design and development include selection of cryptographically strong random number generation.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices explicitly require cryptographically strong RNG selection and usage in security contexts.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Mandates use of approved cryptographic controls, directly requiring cryptographically strong RNGs.
Security testing can detect use of weak random number generators.
Secure SDLC processes should catch weak PRNG usage during design and code review.
Application security requirements can specify cryptographically strong random number generation.
Secure engineering principles include selection of appropriate cryptographic primitives.
Secure coding standards prohibit use of weak PRNGs in security contexts.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (3 rules)
- V-248524 OL 8 must implement NIST FIPS-validated cryptography for the following: To provision digital signatures, to generate cryptographic hashes, and to protect data requiring data-at-rest protections in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards. prevents CWE-340
- V-248563 The OL 8 SSH server must be configured to use strong entropy. prevents CWE-338
- V-248600 OL 8 must have the packages required to use the hardware random number generator entropy gatherer service. prevents CWE-340
RHEL 7 (1 rule)
- V-204497 The Red Hat Enterprise Linux operating system must implement NIST FIPS-validated cryptography for the following: to provision digital signatures, to generate cryptographic hashes, and to protect data requiring data-at-rest protections in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards. prevents CWE-340
RHEL 8 (2 rules)
- V-230253 RHEL 8 must ensure the SSH server uses strong entropy. prevents CWE-338
- V-244527 RHEL 8 must have the packages required to use the hardware random number generator entropy gatherer service. prevents CWE-340
Ubuntu 22.04 (1 rule)
- V-260650 Ubuntu 22.04 LTS must implement NIST FIPS-validated cryptography to protect classified information and for the following: To provision digital signatures, to generate cryptographic hashes, and to protect unclassified information requiring confidentiality and cryptographic protection in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards. prevents CWE-338