CVE-2026-61500 in HFS
Summary
by MITRE • 07/13/2026
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.
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Analysis
by VulDB Data Team • 07/13/2026
This vulnerability exists in Rejetto HFS versions 3.0.0 through 3.2.0 where the session cookie signing key is generated using the non-cryptographic Math.random() function instead of a cryptographically secure random number generator. The flaw stems from the predictable nature of pseudo-random number generators and their susceptibility to state reconstruction attacks. During the authentication process, the system exposes outputs from the same Math.random() generator to unauthenticated clients through login responses, creating a direct pathway for attackers to gather sufficient entropy data.
The technical implementation of this vulnerability combines multiple weaknesses that amplify its impact. The use of Math.random() for cryptographic purposes violates fundamental security principles and directly maps to CWE-330, which addresses the use of insufficiently random values in security contexts. When unauthenticated users interact with the login mechanism, they inadvertently provide attackers with multiple outputs from the same pseudo-random generator, effectively creating a side-channel attack vector that bypasses traditional authentication barriers.
The operational impact of this vulnerability is catastrophic as it enables remote code execution through a simple session forgery attack. An attacker needs only to collect a small number of login responses containing the exposed random values, then reconstruct the internal state of the Math.random() generator using standard statistical analysis techniques. Once the generator state is recovered, the attacker can derive the session cookie signing key and create valid administrator session cookies without requiring any valid credentials or knowledge of user accounts.
The attack pattern follows established methodologies from the MITRE ATT&CK framework, specifically mapping to T1566 for credential access and T1059 for execution through server_code configuration features. The vulnerability allows attackers to escalate privileges from unauthenticated access to full administrative control, enabling them to execute arbitrary code on the target system. This represents a critical privilege escalation path that bypasses all standard authentication mechanisms.
Mitigation strategies must address both the immediate cryptographic weakness and the information disclosure issue. Organizations should immediately upgrade to Rejetto HFS version 3.2.1 or later where the vulnerability has been patched, implementing proper cryptographic random number generation using cryptographically secure alternatives such as crypto.getRandomValues() or similar secure randomness functions. Network segmentation and monitoring of login attempts can help detect exploitation attempts, while disabling unnecessary server_code configuration features reduces the attack surface for successful exploitation. The fundamental lesson here emphasizes the critical importance of using cryptographically secure random number generators for security-sensitive operations and avoiding predictable pseudo-random sequences in authentication contexts.