# CVE-2026-27447: OpenPrinting CUPS authorization bypass in cupsd via case-insensitive comparison

Source: https://junglewise.ai/threats/cve-2026-27447-openprinting-cups-authorization-bypass-in-cupsd-via-case  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-03. Updated: 2026-07-25  
License: CC BY 4.0 with a link back

CVE-2026-27447 · Severity: medium · CVSS 4.8 · Published 2026-04-03

OpenPrinting CUPS is a widely used printing system for Linux and Unix-like operating systems that manages print jobs and printer configurations. A security flaw allows a user to bypass permission checks if their username is a different-case version of an authorized administrator's name (for example, 'bob' gaining the rights of 'BOB'). This could allow an unauthorized person to manage printers, view sensitive documents, or modify system-wide printing settings.

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

## Quick answers

**Is CVE-2026-27447 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-27447 being exploited in the wild.

**How severe is CVE-2026-27447?** Medium severity, with a CVSS score of 4.8, published 3 April 2026.

**Which products and versions are affected?** OpenPrinting Cups <= 2.4.16.

**Is there a fix for CVE-2026-27447?** A patch was published on 2026-04-03: Fix committed to master branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-27447 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-27447?** 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

An authorization bypass exists in the CUPS daemon (cupsd) within the `scheduler/auth.c` component. The vulnerability stems from the use of case-insensitive string comparison (via `_cups_strcasecmp`) when validating if a requesting user belongs to an authorized group, such as 'lpadmin'. On Linux systems where usernames are case-sensitive, an attacker can create or use an account that differs only by case from an authorized user to gain elevated privileges. This allows unauthorized access to restricted operations including printer management and configuration modification. The issue is addressed in version 2.4.17.

## Affected products

- OpenPrinting CUPS <= 2.4.16

## Timeline

- 2026-03-31: advisory: GitHub Security Advisory GHSA-v987-m8hp-phj9 published
- 2026-04-03: disclosed: CVE-2026-27447 published
- 2026-04-03: patched: Fix committed to master branch

## References

- [https://github.com/OpenPrinting/cups/commit/88516bf6d9e34cef7a64a704b856b837f70cd220](https://github.com/OpenPrinting/cups/commit/88516bf6d9e34cef7a64a704b856b837f70cd220)
- [https://github.com/OpenPrinting/cups/security/advisories/GHSA-v987-m8hp-phj9](https://github.com/OpenPrinting/cups/security/advisories/GHSA-v987-m8hp-phj9)

## Related threats

- [OpenPrinting CUPS path traversal in banner processing](https://junglewise.ai/threats/cve-2026-61702-openprinting-cups-is-an-open-source-printing-system-for-linux-and)
- [OpenPrinting CUPS symlink-based file truncation in scheduler](https://junglewise.ai/threats/cve-2026-55480-openprinting-cups-is-an-open-source-printing-system-for-linux-and)
- [CUPS null pointer dereference in IPP job ticket handling](https://junglewise.ai/threats/cve-2026-107655-a-flaw-was-found-in-cups-when-processing-embedded-job-ticket)
- [OpenPrinting CUPS NULL pointer dereference in cupsdCheckJobs](https://junglewise.ai/threats/cve-2026-107888-openprinting-cups-before-2-4-20-contains-a-null-pointer)
- [CUPS scheduler case-insensitive username comparison in ACL validation](https://junglewise.ai/threats/cve-2026-87876-cups-scheduler-case-insensitive-username-comparison-in-acl)