{"id":"CVE-2026-81638","summary":"Non-canonical ULID spellings are accepted and alias to the same record in ash_double_entry","details":"Improper Handling of Alternate Encoding vulnerability in ash-project ash_double_entry allows an attacker to submit several distinct string spellings of the same identifier.\n\nAshDoubleEntry.ULID renders a 128-bit ULID as 26 Crockford base-32 characters, but the first character encodes only 3 bits, so canonical values are 0 to 7. decode/1 in lib/ulid.ex masks the first character to its low 3 bits and valid?/1 accepts all 32 characters in that position, so 0..., 8..., G... and R... decode to the identical 16-byte value and resolve to the same row. When the type is exposed as a public ID over an HTTP or API boundary, an attacker-supplied ID can be spelled differently from the record it actually reads or writes, desynchronizing or bypassing string-level checks such as idempotency and deduplication keys, deny-lists, audit correlation, or signatures computed over the submitted ID.\n\nThis issue affects ash_double_entry: from 0.1.0 before 1.0.19.","aliases":["EEF-CVE-2026-81638","GHSA-qxp2-vgp9-268q"],"modified":"2026-09-10T03:30:44.236271399Z","published":"2026-09-07T22:33:29.297Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81638.json","unresolved_ranges":[{"extracted_events":[{"introduced":"1e5f7ce8ff25f519c904731a29eb1258324e561a"},{"fixed":"d3e688d300a581ae214b3ca7d95ef4de63fbb050"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"EEF","cwe_ids":["CWE-173"]},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-81638.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-81638"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81638.json"},{"type":"ADVISORY","url":"https://github.com/ash-project/ash_double_entry/security/advisories/GHSA-qxp2-vgp9-268q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81638"},{"type":"FIX","url":"https://github.com/ash-project/ash_double_entry/commit/d3e688d300a581ae214b3ca7d95ef4de63fbb050"},{"type":"PACKAGE","url":"https://github.com/ash-project/ash_double_entry"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/ash-project/ash_double_entry","events":[{"introduced":"617f6c2cd7eb1ffd5b71701e76f9c3700e0ae415"},{"fixed":"038e2fa8b1b61c94f39a8d6e494912eb6c0073b8"},{"fixed":"d3e688d300a581ae214b3ca7d95ef4de63fbb050"}],"database_specific":{"extracted_events":[{"introduced":"0.1.0"},{"fixed":"1.0.19"}],"source":["DESCRIPTION","REFERENCES"]}}],"versions":["v1.0.18","v1.0.17","v1.0.16","v1.0.15","v1.0.14","v1.0.13","v1.0.12","v1.0.11","v1.0.10","v1.0.9","v1.0.8","v1.0.7","v1.0.6","v1.0.5","v1.0.4","v1.0.3","v1.0.2","v1.0.1","v1.0.0","v1.0.0-rc.1","v1.0.0-rc.0","v0.2.4","v0.2.3","v0.2.2","v0.2.1","v0.2.0","v0.1.2","v0.1.1","v0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81638.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N"}]}