# CVE-2026-66091: Unauthenticated IDOR Enables Disclosure of Other Users’ last-known details


- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 29 Oct 2026
- **Updated:** 29 Oct 2026
- **Also known as:** GHSA-gj26-grcq-vm8j, GHSA-mxj9-pmpw-j4xw

## What is CVE-2026-66091?

CVE-2026-66091 is a medium-severity vulnerability in Apereo Foundation openEQUELLA, published on 29 Oct 2026. 

### Official description

In openEQUELLA before 2026.1, the GET /api/userquery/userinfobackup endpoint performs no authentication or authorisation check. An unauthenticated attacker who supplies another user's uniqueId can retrieve that user's stored personal details (username, first name, last name and email address) within the same institution.

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

## Which versions are affected by CVE-2026-66091?


## How do I fix CVE-2026-66091?

No fix has been published for CVE-2026-66091 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-66091 being exploited?

There is no known exploitation of CVE-2026-66091 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-66091 and fix it if it is affected.

What it is: CVE-2026-66091 is a medium-severity vulnerability in Apereo Foundation openEQUELLA, published on 29 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-66091 in the wild and no public exploit code.

Affected product: Apereo Foundation openEQUELLA. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-66091/ (Markdown: https://insights.sbomify.com/CVE-2026-66091/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-66091
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-66091
- OSV: https://osv.dev/vulnerability/CVE-2026-66091

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-66091/
Summaries are generated and may contain mistakes; the official description above is the record.