Media ContentProvider URIs used for opening attachments in other apps were generated sequentially prior to WhatsApp for Android v2.20.185, which could have allowed a malicious third party app chosen to open the file to guess the URIs for previously opened attachments until the opener app is terminated.
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 |
| Whatsapp |
Whatsapp |
* |
2.20.185 (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