Vulnerability Description
calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to version 9.4.0, the calibre Content Server's brute-force protection mechanism uses a ban key derived from both `remote_addr` and the `X-Forwarded-For` header. Since the `X-Forwarded-For` header is read directly from the HTTP request without any validation or trusted-proxy configuration, an attacker can bypass IP-based bans by simply changing or adding this header, rendering the brute-force protection completely ineffective. This is particularly dangerous for calibre servers exposed to the internet, where brute-force protection is the primary defense against credential stuffing and password guessing attacks. Version 9.4.0 contains a fix for the issue.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Calibre-Ebook | Calibre | < 9.4.0 |
Related Weaknesses (CWE)
References
- https://github.com/kovidgoyal/calibre/security/advisories/GHSA-vhxc-r7v8-2xrwExploitVendor Advisory
FAQ
What is CVE-2026-27824?
CVE-2026-27824 is a vulnerability with a CVSS score of 5.3 (MEDIUM). calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to version 9.4.0, the calibre Content Server's brute-force protection mechanism uses a ban ke...
How severe is CVE-2026-27824?
CVE-2026-27824 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-27824?
Check the references section above for vendor advisories and patch information. Affected products include: Calibre-Ebook Calibre.