CVE-2026-55736 ash-project CVE debrief

Who should care

Developers and administrators using ash-project ash versions between 3.0.0 and 3.29.3 should be aware of this vulnerability. This issue could allow attackers to inject values for private action arguments, potentially leading to unauthorized actions or data modifications. Applications that use private action arguments for authorization or record ownership are particularly at risk.

Technical summary

The vulnerability arises from incomplete filtering of private arguments in Ash changesets. When building a changeset from a parameter map, Ash is supposed to filter out private arguments. However, this filtering fails when the parameter key is a binary (string), which is common for user-supplied input. In the regular changeset path (for_create, for_update, for_destroy), private arguments are only stripped when the parameter key is an atom. In atomic paths (Ash.Changeset.fully_atomic_changeset/4, atomic and bulk updates), private arguments are not stripped at all, regardless of whether the key is an atom or a binary. This allows attackers to set values for private action arguments, which could be used for malicious purposes such as privilege escalation or data tampering.

Defensive priority

Medium priority should be given to addressing this vulnerability, as it could lead to integrity violations or privilege escalation. The CVSS score of 5.9 indicates a medium severity level.

Recommended defensive actions

• Upgrade ash-project ash to version 3.29.3 or later to fix the vulnerability.
• Review application code to identify and protect sensitive private action arguments.
• Implement additional input validation and sanitization for user-supplied parameters.
• Monitor application logs for suspicious activity related to private action arguments.
• Consider implementing compensating controls, such as role-based access control, to mitigate potential impacts.

Evidence notes

The CVE record and NVD detail provide official information about the vulnerability. Additional sources, including the ash-project ash advisory and OSV vulnerability report, offer further context and technical details. The CVE was published on 2026-06-23 and modified on 2026-06-25.

Official resources