CVE-2026-3255

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BaseFortify

Publication date: 2026-02-27

Last updated on: 2026-03-04

Assigner: CPANSec

Description

HTTP::Session2 versions before 1.12 for Perl for Perl may generate weak session ids using the rand() function. The HTTP::Session2 session id generator returns a SHA-1 hash seeded with the built-in rand function, the 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. HTTP::Session2 after version 1.02 will attempt to use the /dev/urandom device to generate a session id, but if the device is unavailable (for example, under Windows), then it will revert to the insecure method described above.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-02-27

Last Modified

2026-03-04

Generated

2026-07-26

AI Q&A

2026-02-27

EPSS Evaluated

2026-07-25

NVD

CVE-2026-3255

EUVD

EUVD-2026-9063

Affected Vendors & Products

Vendor	Product	Version / Range
tokuhirom	http	to 1.12 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-340	The product uses a scheme that generates numbers or identifiers that are more predictable than required.
CWE-338	The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.

Attack-Flow Graph

Executive Summary

This vulnerability exists in HTTP::Session2 versions before 1.12 for Perl, where the session ID generator uses the built-in rand() function to create session IDs. The rand() function is not suitable for cryptographic purposes, resulting in weak session IDs.

The session ID is generated by hashing a combination of the rand() output, the epoch time, and the process ID (PID) using SHA-1. However, the PID comes from a small set of numbers, and the epoch time can be guessed or leaked, making the session IDs predictable.

Although versions after 1.02 try to use /dev/urandom for better randomness, if this device is unavailable (such as on Windows systems), the insecure method using rand() is still used.

Detection Guidance

I don't know

Impact Analysis

The use of weak session IDs can allow attackers to predict or guess valid session identifiers, potentially enabling session hijacking.

If an attacker can guess a session ID, they may gain unauthorized access to a user's session, leading to data exposure, privilege escalation, or unauthorized actions within the affected application.

Compliance Impact

I don't know

Mitigation Strategies

To mitigate this vulnerability, upgrade HTTP::Session2 to version 1.12 or later, where the session id generation no longer relies on the insecure rand() function.

If upgrading is not immediately possible, ensure that the /dev/urandom device is available and used for session id generation, as HTTP::Session2 after version 1.02 attempts to use it before falling back to the insecure method.

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