# CVE-2026-87876: Auth bypass in Red Hat Enterprise Linux 10

> Attackers can bypass username-based access controls in CUPS scheduler paths due to case-insensitive comparisons, potentially accessing restricted printer resources.

- **Severity:** Low 3.0 (`CVSS:3.1/AV:A/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 9 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-100923, BELL-CVE-2026-87876, DEBIAN-CVE-2026-87876, ECHO-0636-b260-0d3d, GHSA-r8jp-q6fh-g5r2, RHSA-2026:67568, UBUNTU-CVE-2026-87876

## What is CVE-2026-87876?

CVE-2026-87876 is a low-severity authentication bypass vulnerability in Red Hat Enterprise Linux 10, published on 9 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Two case-insensitive comparisons on request-derived usernames outside the main authorization path in CUPS's scheduler (printer ACL validation and private-attribute filtering) could allow bypass of username-based access controls in certain configurations.

Weakness: CWE-178 (Improper Handling of Case Sensitivity)

## Which versions are affected by CVE-2026-87876?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `cups` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |
| `cups-client` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |
| `cups-devel` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |
| `cups-filesystem` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |
| `cups-ipptool` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |
| `cups-libs` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |
| `cups-lpd` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |
| `cups-printerapp` | Red Hat:hummingbird:1 | All versions | 0:2.4.19-4.2.hum1 |

## How do I fix CVE-2026-87876?

Apply the vendor's patch.

## Is CVE-2026-87876 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87876 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-87876 and fix it if it is affected.

What it is: CVE-2026-87876 is a low-severity authentication bypass vulnerability in Red Hat Enterprise Linux 10, published on 9 Sep 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87876 exists.

Affected product: Red Hat Enterprise Linux 10. 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-2026-87876/ (Markdown: https://insights.sbomify.com/CVE-2026-87876/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-87876
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-87876
- OSV: https://osv.dev/vulnerability/CVE-2026-87876

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-87876/
Summaries are generated and may contain mistakes; the official description above is the record.