kovidgoyal calibre up to 9.9.x Template Formatter exec os command injection

Summaryinfo

A vulnerability classified as critical was found in kovidgoyal calibre up to 9.9.x. Affected by this vulnerability is the function exec of the component Template Formatter. Executing a manipulation can lead to os command injection. The identification of this vulnerability is CVE-2026-53511. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in kovidgoyal calibre up to 9.9.x. It has been declared as critical. This vulnerability affects the function exec of the component Template Formatter. The manipulation with an unknown input leads to a os command injection vulnerability. The CWE definition for the vulnerability is CWE-78. The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

calibre is an e-book manager. Prior to 9.10.0, a malicious EPUB, OPF, or PDF file can execute arbitrary Python code when its metadata is read by calibre, including through Add books or Edit books, by embedding a custom column definition with a python: template in calibre:user_metadata that is passed unsanitized to exec() in the template formatter. This issue is fixed in version 9.10.0.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-53511 since 06/09/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1202.

Upgrading to version 9.10.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-42102). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• kovidgoyal

Name

• calibre

Version

• 9.0
• 9.1
• 9.2
• 9.3
• 9.4
• 9.5
• 9.6
• 9.7
• 9.8
• 9.9

Website

• Product: https://github.com/kovidgoyal/calibre/

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Once again VulDB remains the best source for vulnerability data.

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