CVE-2026-27824
calibre has IP Ban Bypass via X-Forwarded-For Header Spoofing
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
calibre has IP Ban Bypass via X-Forwarded-For Header Spoofing
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.
- Record
CVE-2026-27824- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-307, CWE-346
- Updated
- 2026-11-02
EUVDEUVD-2026-9057
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.
- Record
EUVD-2026-9057- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-27824- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-307, CWE-346
- Updated
- 2026-11-02
OSV
calibre has IP Ban Bypass via X-Forwarded-For Header Spoofing
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.
- Record
CVE-2026-27824- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-307, CWE-346
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-27824
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.
- Record
DEBIAN-CVE-2026-27824- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-27824
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.
- Record
UBUNTU-CVE-2026-27824- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
OSVopenSUSE-SU-2026:10587-1 No score
calibre-9.7.0-1.1 on GA media
These are all security issues fixed in the calibre-9.7.0-1.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:10587-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
calibreDebian:12 |
before 6.13.0+repack-2+deb12u6, plus listed versions 6.13.0+repack-26.13.0+repack-2+deb12u16.13.0+repack-2+deb12u26.13.0+repack-2+deb12u36.13.0+repack-2+deb12u46.13.0+repack-2+deb12u5 |
6.13.0+repack-2+deb12u6 |
calibreDebian:13 |
before 8.5.0+ds-1+deb13u2, plus listed versions 8.5.0+ds-18.5.0+ds-1+deb13u1 |
8.5.0+ds-1+deb13u2 |
calibreDebian:14 |
before 9.4.0+ds+~0.10.5-1, plus listed versions 8.10.0+ds-18.10.0+ds-28.10.0+ds-38.11.0+ds+~0.10.5-18.11.1+ds+~0.10.5-1 Show 36 moreShow less8.11.1+ds+~0.10.5-28.11.1+ds+~0.10.5-38.12.0+ds+~0.10.5-18.13.0+ds+~0.10.5-18.13.0+ds+~0.10.5-28.13.0+ds+~0.10.5-38.14.0+ds+~0.10.5-18.14.0+ds+~0.10.5-1~bpo13+18.15.0+ds+~0.10.5-18.15.0+ds+~0.10.5-1~bpo13+18.15.0+ds+~0.10.5-28.16.0+ds+~0.10.5-18.16.0+ds+~0.10.5-28.16.1+ds+~0.10.5-18.16.2+ds+~0.10.5-18.16.2+ds+~0.10.5-28.16.2+ds+~0.10.5-38.16.2+ds+~0.10.5-3~bpo13+18.5.0+ds-18.6.0+ds-18.7.0+ds-18.8.0+ds-18.8.0+ds-28.8.0+ds-2+gcc158.8.0+ds-38.9.0+ds-18.9.0+ds-28.9.0+ds-38.9.0+ds-49.0.0+ds+~0.10.5-19.1.0+ds+~0.10.5-19.2.0+ds+~0.10.5-19.2.1+ds+~0.10.5-19.2.1+ds+~0.10.5-29.3.0+ds+~0.10.5-19.3.1+ds+~0.10.5-1 |
9.4.0+ds+~0.10.5-1 |
calibreUbuntu:16.04:LTS |
All versions, plus listed versions 2.33.0+dfsg-1build12.38.0+dfsg-12.45.0+dfsg-12.45.0+dfsg-1build12.48.0+dfsg-1 Show 4 moreShow less2.48.0+dfsg-1build12.54.0+dfsg-12.55.0+dfsg-12.55.0+dfsg-1ubuntu0.2 |
None known |
calibreUbuntu:18.04:LTS |
All versions, plus listed versions 3.7.0+dfsg-23.7.0+dfsg-2build13.12.0+dfsg-13.13.0+dfsg-13.14.0+dfsg-1 Show 10 moreShow less3.15.0.1+dfsg-13.16.0+dfsg-13.16.0+dfsg-1build13.17.0+dfsg-13.17.0+dfsg-23.18.0+dfsg-1build13.19.0+dfsg-13.20.0+dfsg-13.21.0+dfsg-13.21.0+dfsg-1build1 |
None known |
calibreUbuntu:20.04:LTS |
All versions, plus listed versions 3.46.0+dfsg-14.2.0+dfsg-24.3.0+dfsg-14.3.0+dfsg-24.4.0+dfsg-1 Show 14 moreShow less4.5.0+dfsg-14.5.0+dfsg-24.5.0+dfsg-34.6.0+dfsg-14.7.0+dfsg-14.99.3+dfsg-24.99.4+dfsg-14.99.4+dfsg-1build14.99.4+dfsg+really4.10.0+py3-24.99.4+dfsg+really4.11.2-14.99.4+dfsg+really4.11.2-1build14.99.4+dfsg+really4.12.0-14.99.4+dfsg+really4.12.0-1build14.99.4+dfsg+really4.12.0-1ubuntu1 |
None known |
calibreUbuntu:22.04:LTS |
All versions, plus listed versions 5.25.0+dfsg-25.33.2+dfsg-15.34.0+dfsg-15.35.0+dfsg-1ubuntu25.37.0+dfsg-15.37.0+dfsg-1build1 |
None known |
calibreUbuntu:24.04:LTS |
All versions, plus listed versions 6.24.0+ds-16.29.0+ds-17.0.0+ds-17.1.0+ds-17.1.0+ds-2 Show 9 moreShow less7.2.0+ds-17.2.0+ds-1build17.3.0+ds-17.4.0+ds-17.5.1+ds-17.5.1+ds-27.5.1+ds-37.6.0+ds-17.6.0+ds-1build1 |
None known |
calibreUbuntu:25.10 |
All versions, plus listed versions 7.26.0+ds-4build18.3.0+ds-18.4.0+ds-18.5.0+ds-18.6.0+ds-1 Show 4 moreShow less8.7.0+ds-18.8.0+ds-28.8.0+ds-38.8.0+ds-3build1 |
None known |
calibreUbuntu:26.10 |
All versions, plus listed versions 9.2.1+ds+~0.10.5-2build19.9.0+ds+~0.10.6-19.11.0+ds+~0.10.6-19.11.0+ds+~0.10.6-29.13.0+ds+~0.10.6-19.14.0+ds+~0.10.6-2build1 |
None known |
calibreUbuntu:26.04:LTS |
All versions, plus listed versions 8.8.0+ds-3build18.13.0+ds+~0.10.5-38.14.0+ds+~0.10.5-18.15.0+ds+~0.10.5-18.16.0+ds+~0.10.5-2 Show 4 moreShow less8.16.2+ds+~0.10.5-18.16.2+ds+~0.10.5-28.16.2+ds+~0.10.5-39.2.1+ds+~0.10.5-2build1 |
None known |
calibreopenSUSE:Tumbleweed From an advisory covering 10 CVEs |
before 9.7.0-1.1 | 9.7.0-1.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-27824 is a medium vulnerability (CVSS 5.3) in Calibre-ebook Calibre, published February 27, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.17%, the 6th percentile. Fixed in calibre 6.13.0+repack-2+deb12u6.
References
github.com/kovidgoyal/calibre/security/advisories/GHSA-vhxc-r7v8-2xrw
nvd.nist.gov/vuln/detail/CVE-2026-27824
security-tracker.debian.org/tracker/CVE-2026-27824
ubuntu.com/security/CVE-2026-27824
cve.org/CVERecord?id=CVE-2026-27824
Show 10 moreShow less
suse.com/security/cve/CVE-2026-25635