# CVE-2026-87876: CUPS scheduler case-insensitive username comparison in ACL validation

Source: https://junglewise.ai/threats/cve-2026-87876-cups-scheduler-case-insensitive-username-comparison-in-acl  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-87876 · Severity: low · CVSS 3 · Published 2026-09-09

CUPS is a widely-used printing system that manages access to network printers through username-based access controls. A flaw in how the scheduler compares usernames allows attackers in certain configurations to bypass printer access restrictions and unauthorized filtering of private attributes by exploiting case-sensitive/insensitive comparison logic, potentially gaining access to restricted print queues or viewing sensitive print job metadata.

Technologies: [OpenPrinting Cups](https://junglewise.ai/threats/technologies/cups). Vendors: [OpenPrinting](https://junglewise.ai/threats/vendors/openprinting).

## Quick answers

**Is CVE-2026-87876 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-87876 being exploited in the wild.

**How severe is CVE-2026-87876?** Low severity, with a CVSS score of 3, published 9 September 2026.

**Which products and versions are affected?** OpenPrinting Cups <UNKNOWN>.

**Is there a fix for CVE-2026-87876?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-87876 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-87876?** Check whether you run OpenPrinting Cups at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in CUPS's scheduler due to two case-insensitive string comparisons performed on request-derived usernames outside the main authorization code path. These comparisons occur in printer ACL (Access Control List) validation and private-attribute filtering logic. An attacker can craft usernames that differ only in case (e.g., "admin" vs "Admin") to bypass username-based access controls, provided the system is configured to enforce such controls. The flaw requires network access to a CUPS printer server and knowledge of valid usernames. A patch addressing the comparison logic is expected from the CUPS maintainers.

## Affected products

- OpenPrinting CUPS <UNKNOWN>

## Timeline

- 2026-09-09: disclosed

## References

- [https://catalog.redhat.com/software/containers/](https://catalog.redhat.com/software/containers/)
- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)

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