Listen to this Post
The vulnerability exists in the `SecurityIO.groovy` class where data is encrypted using AES/CBC/PKCS5Padding. CBC mode alone provides confidentiality but not integrity or authenticity. This allows an attacker to manipulate ciphertext blocks. The system uses an external SHA-256 checksum on the encrypted data, which is verified before decryption, but the cryptographic primitive itself is malleable. Without built-in authentication like an HMAC or GCM tag, the decryption oracle can be probed. By submitting manipulated ciphertext and observing the system’s response (like checksum failure vs. padding error), an attacker can perform a padding oracle attack. This could potentially allow the recovery of plaintext without the key, one byte at a time. The attack complexity is high in Jervis’s specific context due to the RSA-wrapped keys and mandatory checksum, but the underlying cryptographic flaw is present in the direct use of the vulnerable AES/CBC methods.
Platform: Jervis
Version: Pre-2.2
Vulnerability: Missing Authentication
Severity: Critical
date: 2026-01-13
Prediction: 2026-01-20
What Undercode Say:
// Vulnerable Code Lines (AES/CBC/PKCS5Padding):
Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
...
cipher.init(Cipher.ENCRYPT_MODE, secret, ivSpec)
// Patch migrates to:
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding")
How Exploit:
Attacker intercepts/modifies ciphertext. Attacker sends manipulated data. System decrypts, reveals padding error. Attacker analyzes timing/response differences. Attacker iterates to guess plaintext bytes.
Protection from this CVE:
Upgrade to Jervis 2.2. Use AES-GCM mode. Implement authenticated encryption. Never use CBC alone.
Impact:
Plaintext decryption possible. Ciphertext manipulation feasible. Impact limited internally. Tokens expire quickly.
🎯Let’s Practice Exploiting & Learn Patching For Free:
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
