CVE-2026-61500

Description

Rejetto HFS 3.0.0 through 3.2.0 derives its session-cookie signing key from the non-cryptographic Math.random() generator and discloses outputs of the same generator to unauthenticated clients during login. A remote attacker can collect a small number of login responses, reconstruct the generator's state, recover the signing key, and forge a valid administrator session cookie, leading to full administrative access and remote code execution via the server_code configuration feature.

CVSS Metrics

• v4.0•CRITICAL•Score: 9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
• v3.1•CRITICAL•Score: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Techniques & Countermeasures

• CWE-338•Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

  The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.

Affected Systems

• rejetto•hfs

  ≥ 3.0.0, < 3.2.1

References (2)

• https://github.com/rejetto/hfs/releases/tag/v3.2.1
• https://www.vulncheck.com/advisories/rejetto-hfs-session-forgery-via-predictable-signing-key