Executive brief
Ash Authentication's audit log IP address pseudonymization uses weak hashing that allows attackers with access to audit logs to recover the original client IP addresses. The default salt is published in the source code and predictable, the hash is unkeyed, and the IPv4 space is small enough to brute-force completely. Applications relying on this privacy mode for data protection are exposed to IP address disclosure.
Technical details
The vulnerability exists in AshAuthentication.AddOn.AuditLog.IpPrivacy.hash_ip/1, which computes a SHA-256 hash of a predictable or default salt concatenated with an IP address, then truncates to 16 hex characters. The salt defaults to the hardcoded constant "default-salt-change-in-production" when not configured, and even when configured, is not application-secret. Because the entire IPv4 address space is only 2^32 values and SHA-256 is computationally fast, an attacker with read access to the audit store can precompute a rainbow table of all possible hashed IPv4 addresses and trivially reverse any stored hash. The 16-character truncation does not meaningfully increase the attack complexity. Affected versions are 4.12.0 through 4.14.x and 5.0.0-rc.0 through 5.0.0-rc.13.
Affected products
- team-alembic AshAuthentication 4.12.0 through 4.14.x and 5.0.0-rc.0 through 5.0.0-rc.13
Timeline
- 2026-09-17: disclosed