CVE-2026-25731 Calibre Affected by Arbitrary Code Execution via Server-Side Template Injection in Calibre HTML Export

High 7.8 Published 6 Feb 2026 Updated 6 Feb 2026

Attacker can execute arbitrary code by tricking a user into converting an ebook with a malicious custom template file.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2026-25731?

CVE-2026-25731 is a high-severity code injection vulnerability in kovidgoyal calibre, published on 6 Feb 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

calibre is an e-book manager. Prior to 9.2.0, a Server-Side Template Injection (SSTI) vulnerability in Calibre's Templite templating engine allows arbitrary code execution when a user converts an ebook using a malicious custom template file via the --template-html or --template-html-index command-line options. This vulnerability is fixed in 9.2.0.

Weakness: CWE-1336

Which versions are affected by CVE-2026-25731?

It affects 1 product.

Products include Calibre-Ebook Calibre.

How do I fix CVE-2026-25731?

Upgrade to a fixed version.

Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.

Is CVE-2026-25731 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-25731 exists.

Public exploit code: 1 proofs of concept on GitHub.

Sources

Also known as DEBIAN-CVE-2026-25731, GHSA-xrh9-w7qx-3gcc, UBUNTU-CVE-2026-25731.