Description

CAT uses Java String.hashCode as the sole integrity check for session cookies without server-side keying, allowing attackers to forge valid checksums offline. Attackers can set the x-forwarded-for header to bypass IP binding validation and create admin sessions with full configuration access.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-03T15:17:39.433Z",
  "pubdate": "2026-09-03T15:17:39.433Z",
  "executiveSummary": "The CAT application exhibits a critical vulnerability in its session management architecture, specifically regarding the integrity verification of session cookies.\nThe system relies on the Java String.hashCode() method as the exclusive mechanism for validating session cookie integrity, lacking any server-side secret keying or cryptographic signing.\nThis design flaw allows unauthorized actors to perform offline checksum generation, enabling the creation of arbitrary session cookies.\nFurthermore, the application incorrectly validates IP binding by trusting the x-forwarded-for HTTP header, which can be easily spoofed by malicious users to bypass network-level restrictions.\nThe confluence of these vulnerabilities grants an attacker the ability to forge administrative session tokens.\nSuccessful exploitation results in full administrative access to the system, allowing for complete configuration manipulation and unauthorized access to system resources.\nThe vulnerability requires no prior authentication and can be exploited over the network, posing a severe risk to the confidentiality, integrity, and availability of the CAT instance.",
  "technicalDetails": "The core vulnerability lies in the reliance on Java String.hashCode() for security-sensitive integrity checks. The hashCode() function is deterministic, non-cryptographic, and produces a 32-bit integer that is computationally trivial to invert or collide.\nBecause the application does not employ a server-side secret (HMAC) or a robust digital signature, an attacker can analyze a legitimate session cookie, determine the expected hash for a target payload, and generate valid-looking cookies offline without interacting with the server.\nThe exploitation flow begins with the attacker crafting a malicious session object containing elevated privileges, such as admin-level configuration access flags. The attacker then calculates the corresponding Java String.hashCode() value required by the application's verification logic. By injecting this forged checksum into the session cookie, the attacker bypasses the weak integrity check entirely.\nThe secondary attack vector involves the application's reliance on the x-forwarded-for header for IP binding validation. In typical load-balanced or proxy-heavy environments, this header is user-controllable. By manipulating the x-forwarded-for header in the forged request, the attacker can spoof the origin IP to appear as a trusted or authorized host, effectively neutralizing any IP-based access control lists (ACLs) implemented by CAT.\nThe step-by-step attack flow is as follows: 1) The attacker inspects the application's session handling to identify the structure of the cookie and the role of the hash. 2) The attacker crafts an administrative session payload. 3) The attacker generates a valid hashCode() for the payload. 4) The attacker sends a crafted HTTP request to the CAT server, including the forged session cookie and an injected x-forwarded-for header to masquerade as an authorized IP. 5) The server-side logic accepts the forged hash, performs the vulnerable IP validation check using the spoofed header, and grants the attacker full administrative privileges.\nThe post-exploitation impact is total system compromise, as the attacker gains the ability to modify system configurations, manage users, and potentially execute further commands depending on the underlying privileges of the CAT service account."
}