An authorization bypass in b2evolution allows remote, unauthenticated attackers to predict password reset tokens for any user through the use of a bad randomness function. This allows the attacker to get valid sessions for arbitrary users, and optionally reset their password. Tested and confirmed in a default installation of version 7.2.3. Earlier versions are affected, possibly earlier major versions as well.
Weakness
The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| B2evolution |
B2evolution |
* |
7.2.5 (excluding) |
Potential Mitigations
- Use a well-vetted algorithm that is currently considered to be strong by experts in the field, and select well-tested implementations with adequate length seeds.
- In general, if a pseudo-random number generator is not advertised as being cryptographically secure, then it is probably a statistical PRNG and should not be used in security-sensitive contexts.
- Pseudo-random number generators can produce predictable numbers if the generator is known and the seed can be guessed. A 256-bit seed is a good starting point for producing a “random enough” number.
References