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How the mentioned CVE works:
The vulnerability resides in the token encryption mechanism when the TOKEN_HASH_SECRET environment variable is absent. In tempTokenUtils.ts lines 31-34, the code derives an AES-256-CBC encryption key by hashing either the environment variable or a hardcoded default string ‘Secre$t’ using SHA256. This default value is cryptographically weak and publicly known. The resulting key is used in encryptToken() (called from passport/index.ts line 394) to encrypt sensitive metadata—specifically user IDs and workspace IDs—embedded inside JWT tokens as a ‘meta’ field. Because the secret is not required at startup, many deployments may inadvertently rely on the default. An attacker aware of ‘Secre$t’ can intercept any JWT token, extract the encrypted meta field, and decrypt it using the same key derivation. This reveals internal identifiers that should remain secret. Furthermore, because the encryption lacks authentication (raw AES-CBC), the attacker can modify the decrypted plaintext (e.g., change a user ID to a higher-privileged ID), re-encrypt it with the known key, and replace the original meta field. The JWT signature remains valid as it does not cover the encrypted meta field separately, allowing the attacker to submit a forged token. The .env.example file shows ‘ TOKEN_HASH_SECRET=’popcorn” (commented out), reinforcing the misconception that this secret is optional. No error is thrown when the variable is missing, making the default active. Practical exploitability is medium because the attacker needs network access to a token and knowledge of the default secret. The weakness affects all versions where the code contains this default fallback. The CVSS score would be approximately 6.5 (Medium) due to privilege escalation potential.
dailycve form:
Platform: Kolega.dev
Version: Not specified
Vulnerability: Weak default encryption
Severity: Medium
date: Date not given
Prediction: Expected patch 2026-05-01
What Undercode Say:
Analytics:
Check if TOKEN_HASH_SECRET is set to default grep -r "TOKEN_HASH_SECRET" .env.example Scan for hardcoded 'Secre$t' in source grep -n "Secre\$t" packages/server/src/enterprise/utils/tempTokenUtils.ts Decrypt a JWT meta field using OpenSSL (after extracting base64) echo "encrypted_meta_base64" | base64 -d | openssl enc -d -aes-256-cbc -K $(echo -n 'Secre$t' | sha256sum | cut -d' ' -f1) -iv 0
// Node.js decryption demonstration
const crypto = require('crypto');
const key = crypto.createHash('sha256').update('Secre$t').digest();
const decipher = crypto.createDecipheriv('aes-256-cbc', key, Buffer.alloc(16,0));
let decrypted = decipher.update(encryptedMeta, 'base64', 'utf8');
decrypted += decipher.final('utf8');
console.log(decrypted);
Exploit:
- Intercept a valid JWT token from the application.
2. Extract the ‘meta’ field (Base64-encoded ciphertext).
3. Derive AES-256-CBC key using SHA256 of ‘Secre$t’.
- Decrypt the meta field to obtain plaintext containing user ID and workspace ID.
- Modify the plaintext (e.g., change user ID to “admin” or another target ID).
- Re-encrypt the modified plaintext using the same key and zero IV.
- Replace the original meta field in the JWT with the new ciphertext.
- Send the forged token to the application to escalate privileges.
Protection from this CVE
- Remove the hardcoded default ‘Secre$t’ from source code.
- Enforce that TOKEN_HASH_SECRET is always set in production environment.
- Add startup validation: throw error if TOKEN_HASH_SECRET is missing or weak.
- Use a strong random secret with at least 32 bytes of entropy (e.g.,
openssl rand -base64 32). - Replace AES-CBC with an authenticated encryption mode (e.g., AES-GCM) or add HMAC.
- Rotate all existing tokens after deploying the fix.
Impact:
Token forgery leading to privilege escalation. An attacker can decrypt JWT metadata to leak internal user/workspace IDs, then manipulate and re-encrypt those IDs to impersonate other users or access unauthorized workspaces. This bypasses access controls that rely on the encrypted metadata, potentially allowing data theft, account takeover, or lateral movement within the application. The JWT signature remains intact, making the forged token appear valid to the server.
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Sources:
Reported By: github.com
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