# CVE-2026-53511: Calibre arbitrary code execution via malicious book metadata

Source: https://junglewise.ai/threats/cve-2026-53511-calibre-arbitrary-code-execution-via-malicious-book-metadata  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-07. Updated: 2026-07-07  
License: CC BY 4.0 with a link back

CVE-2026-53511 · Severity: info · CVSS 8.5 · Published 2026-07-07

Calibre, a popular e-book management application, is vulnerable to a security flaw that allows malicious e-book files to execute unauthorized code on a user's computer. By simply adding or editing a specially crafted EPUB, PDF, or OPF file, an attacker can gain the same permissions as the user, potentially leading to data theft or full system compromise. Users should update to version 9.10.0 or later to resolve this issue.

## Quick answers

**Is CVE-2026-53511 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-53511 being exploited in the wild.

**How severe is CVE-2026-53511?** Informational severity, with a CVSS score of 8.5, published 7 July 2026.

**Which products and versions are affected?** Kovid Goyal Calibre < 9.10.0.

**Is there a fix for CVE-2026-53511?** A patch was published on 2026-06-26: Version 9.10.0 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-53511 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2026-53511?** Check whether you run Kovid Goyal Calibre 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

A code injection vulnerability exists in Calibre's template formatter prior to version 9.10.0. The root cause is the unsanitized processing of 'calibre:user_metadata' within EPUB, OPF, or PDF files. When Calibre reads metadata (e.g., during 'Add books' or 'Edit books' operations), it parses custom column definitions via json.loads() and stores them. If a composite custom column contains a 'python:' template, it is passed to the template formatter's safe_format() method, which eventually reaches exec() via compile_python_template(). An attacker can exploit this by providing a malicious e-book file that, when imported or edited, executes arbitrary Python code with the privileges of the Calibre process. The fix involves disallowing Python templates when reading book metadata.

## Affected products

- kovidgoyal calibre < 9.10.0

## Timeline

- 2026-06-26: patched: Version 9.10.0 released
- 2026-06-26: advisory: GitHub Security Advisory published
- 2026-07-07: disclosed: CVE-2026-53511 published to NVD

## References

- [https://github.com/kovidgoyal/calibre/commit/712f4e1ff5c1e798c335bef3bacc4efdee052e9c](https://github.com/kovidgoyal/calibre/commit/712f4e1ff5c1e798c335bef3bacc4efdee052e9c)
- [https://github.com/kovidgoyal/calibre/releases/tag/v9.10.0](https://github.com/kovidgoyal/calibre/releases/tag/v9.10.0)
- [https://github.com/kovidgoyal/calibre/security/advisories/GHSA-2j4m-2q7x-2c47](https://github.com/kovidgoyal/calibre/security/advisories/GHSA-2j4m-2q7x-2c47)