Match regex runs on over-length input in Ash.Type.String, enabling regex denial of service

Summary

Uncontrolled Resource Consumption vulnerability in ash-project ash allows an attacker to force an expensive regular expression to run on input that a length constraint should have already rejected. Ash.Type.String.apply_constraints/2 (lib/ash/type/string.ex) evaluated the :match regex regardless of the min_length and max_length constraints on the same attribute. Because the length check did not gate the regex, an over-length value that the length constraint rejects still had the pattern applied to it, so the length limit that would otherwise bound the work never constrained the regex input. Against a backtracking pattern this yields catastrophic regex evaluation on attacker-sized input, and even a linear pattern runs on arbitrarily large input, consuming CPU per request. The fix skips the :match regex whenever a length constraint is violated, making the two checks order-independent. This issue affects ash: from 0.10.0 before 3.32.2.

Timeline

1. Sep 1, 2026, 3:19 AM UTCCVE published
2. Sep 1, 2026, 1:10 PM UTCCISA SSVC assessment

   Exploitation: poc · Automatable: no · Technical impact: partial

3. Sep 1, 2026, 1:11 PM UTCRecord last updated

Affected versions

• ash

  From 0.10.0 · fixed in 3.32.2

• ash-project/ash

  Version range not reported

References 4