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CVE PROGRAM SOURCE RECORD2.1 Low

CVE-2026-81638

Non-canonical ULID spellings are accepted and alias to the same record in ash_double_entry

Description

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. AshDoubleEntry.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. This issue affects ash_double_entry: from 0.1.0 before 1.0.19.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

ash-project ash_double_entry

Default version status: unaffected

  • 0.1.0 to < 1.0.19affected
pkg:hex/ash_double_entry

ash-project ash_double_entry

Default version status: unaffected

  • 1e5f7ce8ff25f519c904731a29eb1258324e561a to < d3e688d300a581ae214b3ca7d95ef4de63fbb050affected
pkg:github/ash-project/ash_double_entry

References