CVE-2026-82759 Reversible IP address pseudonymisation in AshAuthentication audit log hash mode
Attackers can recover client IP addresses from audit logs due to weak hashing with predictable salts in AshAuthentication.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-82759?
CVE-2026-82759 is a low-severity vulnerability in team-alembic ash_authentication, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Use of a One-Way Hash with a Predictable Salt vulnerability in team-alembic AshAuthentication allows readers of the audit store to recover the client IP addresses that the audit log add-on's :hash privacy mode is meant to pseudonymise.
AshAuthentication.AddOn.AuditLog.IpPrivacy.hash_ip/1 computes a single unkeyed :crypto.hash(:sha256, salt <> ip) and truncates the result to 16 hexadecimal characters. The salt is read from the :audit_log_ip_salt or :secret application config keys, and falls back to the constant "default-salt-change-in-production" published in the library source when neither is set, with nothing warning that the default is in use. The IPv4 space is only 2^32 values and SHA-256 is fast, so the whole hash table is precomputable and every stored value maps back to its source address. Truncating to 16 characters does not help, and even a configured salt leaves the hash cheap enough to enumerate once it leaks.
This issue affects ash_authentication: from 4.12.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.
Weakness: CWE-760
Which versions are affected by CVE-2026-82759?
1 open source package ship an affected version, including ash_authentication.
| Package | Affected | Fixed in |
|---|---|---|
ash_authentication Hex | From 4.12.0 | 4.15.0, 5.0.0-rc.14 |
How do I fix CVE-2026-82759?
Upgrade ash_authentication to a fixed version for your release line: 4.15.0 or 5.0.0-rc.14.
Is CVE-2026-82759 being exploited?
There is no known exploitation of CVE-2026-82759 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-82759, GHSA-cgqj-pcpq-xhfm.