Reversible IP address pseudonymisation in AshAuthentication audit log hash mode
Published Sep 17, 2026 · Updated Sep 17, 2026
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.
Summary
What happened
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.
The record
- CVE
- CVE-2026-82759
- Published
- Sep 17, 2026
- Updated
- Sep 17, 2026
- Vendor
- Alembic
- Product
- Ash Authentication
- Classifications
- Unavailable
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 17, 2026CVE publishedPublication date reported by the CVE source.
- Sep 17, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=255cfc9c0e511b7e0de39f8b3d676ae994fae06c <* changes=[{"at":"d8a9c4b6bde828fdc8346198d5e4f588b5937541","status":"unaffected"},{"at":"c3a6d5fe0d4fd383ea81b0402db0a96638479478","status":"unaffected"}]
- Affected versionversion=4.12.0 <4.15.0
- Affected versionversion=5.0.0-rc.0 <5.0.0-rc.14
What conditions does exploitation require?
What is affected?
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Attacks
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Activity data is delayed. The latest report is Sep 28, 2026.
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