# CVE-2026-82753: Denial of service in ash authentication oauth2 server

> Unauthenticated attackers can exhaust database and memory resources by creating unlimited client rows via the authorize endpoint when CIMD is enabled.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 7 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** EEF-CVE-2026-82753, GHSA-9pv3-wxjm-f846

## What is CVE-2026-82753?

CVE-2026-82753 is a high-severity denial of service vulnerability in ash-project ash_authentication_oauth2_server, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Allocation of Resources Without Limits or Throttling vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to exhaust database storage and memory.

The /authorize endpoint is unauthenticated by design. With Client ID Metadata Documents enabled, resolve_client/3 in AshAuthentication.Oauth2Server.CIMD fetches the document for each new URL-shaped client_id and upserts a client row, with no cap on the number of rows, no expiry or garbage collection, and no length bound on the fetched fields; the document was also placed in CIMD.Cache before validation, so even rejected documents held cache memory until their TTL. An attacker serving valid documents at many distinct URLs creates one permanent client row per URL, each able to carry multi-megabyte strings, growing storage and memory without bound.

This issue affects ash_authentication_oauth2_server: from 0.3.0 before 0.3.1.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-82753?

1 open source package ship an affected version, including ash_authentication_oauth2_server.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ash_authentication_oauth2_server` | Hex | From 0.3.0 | 0.3.1 |

## How do I fix CVE-2026-82753?

Upgrade ash_authentication_oauth2_server to 0.3.1 or later.

## Is CVE-2026-82753 being exploited?

There is no known exploitation of CVE-2026-82753 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82753 and fix it if it is affected.

What it is: CVE-2026-82753 is a high-severity denial of service vulnerability in ash-project ash_authentication_oauth2_server, published on 7 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-82753 in the wild and no public exploit code.

Affected packages and fixed versions:
- ash_authentication_oauth2_server (Hex): affected from 0.3.0; fixed in 0.3.1

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-2026-82753/ (Markdown: https://insights.sbomify.com/CVE-2026-82753/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82753
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82753
- OSV: https://osv.dev/vulnerability/CVE-2026-82753

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82753/
Summaries are generated and may contain mistakes; the official description above is the record.