{"id":"EEF-CVE-2026-82759","summary":"Reversible IP address pseudonymisation in AshAuthentication audit log hash mode","details":"## Summary\n\nUse 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.\n\n`AshAuthentication.AddOn.AuditLog.IpPrivacy.hash_ip/1` computes a single unkeyed `:crypto.hash(:sha256, salt \u003c\u003e 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.\n\nThis 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.\n\n## Configurations\n\nOnly applications that enable the `audit_log` add-on and set its `ip_privacy` mode to `:hash` store the affected value. Other modes (`:none`, `:truncate`, `:exclude`) do not reach `hash_ip/1`.\n\nThe complete break additionally requires the default salt, that is neither `:audit_log_ip_salt` nor `:secret` configured under the `:ash_authentication` application. This is the out-of-the-box state: no warning or error is raised when the hardcoded salt is in use.","aliases":["CVE-2026-82759","GHSA-cgqj-pcpq-xhfm"],"modified":"2026-09-17T13:26:04.053149254Z","published":"2026-09-17T13:08:21.929Z","database_specific":{"cpe_ids":["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-760"],"capec_ids":["CAPEC-112"]},"references":[{"type":"ADVISORY","url":"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-cgqj-pcpq-xhfm"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-82759.html"},{"type":"WEB","url":"https://github.com/team-alembic/ash_authentication/commit/255cfc9c0e511b7e0de39f8b3d676ae994fae06c"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/d8a9c4b6bde828fdc8346198d5e4f588b5937541"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/c3a6d5fe0d4fd383ea81b0402db0a96638479478"},{"type":"PACKAGE","url":"https://hex.pm/packages/ash_authentication"}],"affected":[{"package":{"name":"ash_authentication","ecosystem":"Hex","purl":"pkg:hex/ash_authentication"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.12.0"},{"fixed":"4.15.0"}]},{"type":"SEMVER","events":[{"introduced":"5.0.0-rc.0"},{"fixed":"5.0.0-rc.14"}]}],"versions":["4.12.0","4.13.0","4.13.1","4.13.2","4.13.3","4.13.4","4.13.5","4.13.6","4.13.7","4.14.0","4.14.1","4.14.2","5.0.0-rc.0","5.0.0-rc.1","5.0.0-rc.10","5.0.0-rc.11","5.0.0-rc.12","5.0.0-rc.13","5.0.0-rc.2","5.0.0-rc.3","5.0.0-rc.4","5.0.0-rc.5","5.0.0-rc.6","5.0.0-rc.7","5.0.0-rc.8","5.0.0-rc.9"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-82759.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/team-alembic/ash_authentication","events":[{"introduced":"255cfc9c0e511b7e0de39f8b3d676ae994fae06c"},{"fixed":"d8a9c4b6bde828fdc8346198d5e4f588b5937541"},{"fixed":"c3a6d5fe0d4fd383ea81b0402db0a96638479478"}]}],"versions":["v4.14.2","v5.0.0-rc.13","v4.14.1","v5.0.0-rc.12","v5.0.0-rc.11","v5.0.0-rc.10","v4.14.0","v4.13.7","5.0.0-rc.9","5.0.0-rc.8","v5.0.0-rc.7","v5.0.0-rc.6","v5.0.0-rc.5","v5.0.0-rc.4","v5.0.0-rc.3","v5.0.0-rc.2","v5.0.0-rc.1","v5.0.0-rc.0","v4.13.6","v4.13.5","v4.13.4","v4.13.3","v4.13.2","v4.13.1","v4.13.0","v4.12.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-82759.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"}],"credits":[{"name":"Jonatan Männchen / EEF","type":"ANALYST"},{"name":"James Harton","type":"REMEDIATION_DEVELOPER"},{"name":"Peter Ullrich","type":"REPORTER"}]}