# CVE-2026-81853: AshAdmin composite primary key decoding accepts arbitrary fields, enabling a secret-attribute oracle

> Attackers can brute-force sensitive attributes like API tokens by manipulating composite primary key decoding in AshAdmin, bypassing intended lookup restrictions.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Aug 2026
- **Updated:** 31 Aug 2026
- **Also known as:** EEF-CVE-2026-81853, GHSA-jxr8-hpv2-qp38

## What is CVE-2026-81853?

CVE-2026-81853 is a low-severity authentication bypass vulnerability in ash-project ash_admin, published on 31 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Authorization Bypass Through User-Controlled Key vulnerability in ash-project ash_admin turns a record-lookup URL into an equality oracle over sensitive attributes.

AshAdmin.Helpers.decode_primary_key/2 decodes the composite-primary-key form (Base64 plus ETF) and returns the decoded map verbatim as the lookup filter, without checking that its keys are the resource's primary-key fields. The deserialization guards bound size, block new atoms and funs, and reject nested expressions, but none restricts which fields come back, and :safe still allows any already-interned attribute name. An attacker can therefore encode %{api_token: "guess"} and have it spliced into the lookup filter, brute-forcing a sensitive attribute value (API token, reset token) one equality guess at a time; Map.to_list/1 also accepts structs, yielding a bogus __struct__ key. The fix rejects any decoded key that is not a real primary-key field.

This issue affects ash_admin: from 0.1.0 before 1.3.1.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-81853?

1 open source package ship an affected version, including ash_admin.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_admin` | Hex | From 0.1.0 | 1.3.1 |

## How do I fix CVE-2026-81853?

Upgrade ash_admin to 1.3.1 or later.

## Is CVE-2026-81853 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-81853 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81853 and fix it if it is affected.

What it is: CVE-2026-81853 is a low-severity authentication bypass vulnerability in ash-project ash_admin, published on 31 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-81853 exists.

Affected packages and fixed versions:
- ash_admin (Hex): affected from 0.1.0; fixed in 1.3.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-81853/ (Markdown: https://insights.sbomify.com/CVE-2026-81853/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81853
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81853
- OSV: https://osv.dev/vulnerability/CVE-2026-81853

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81853/
Summaries are generated and may contain mistakes; the official description above is the record.