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

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

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 6 Feb 2026
- **Updated:** 6 Feb 2026
- **Also known as:** DEBIAN-CVE-2026-25731, GHSA-xrh9-w7qx-3gcc, UBUNTU-CVE-2026-25731

## 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 (Improper Neutralization of Special Elements Used in a Template Engine)

## Which versions are affected by CVE-2026-25731?

It affects 1 product.


Products: Calibre-Ebook Calibre.

## How do I fix CVE-2026-25731?

Upgrade to a fixed version.

## 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:

- Proof of Concept for a Server-Side Template Injection (SSTI) vulnerability in Calibre’s Templite engine (GHSA-xrh9-w7qx-3gcc). Demonstrates arbitrary Python code execution via user-supplied HTML export templates in affected versions (≤ 9.1.0). (github_poc): https://github.com/dxlerYT/CVE-2026-25731

## Other vulnerabilities in kovidgoyal calibre

- [CVE-2011-4124](https://insights.sbomify.com/CVE-2011-4124/): Command injection in Calibre (critical 9.8)
- [CVE-2011-4125](https://insights.sbomify.com/CVE-2011-4125/): Privilege escalation in Calibre (critical 9.8)
- [CVE-2026-26064](https://insights.sbomify.com/CVE-2026-26064/): calibre: Path Traversal Vulnerability Enables Arbitrary File Write and Remote Code Execution (critical 9.3)
- [CVE-2026-26065](https://insights.sbomify.com/CVE-2026-26065/): calibre: Path Traversal can Lead to Arbitrary File Write and Potential Code Execution (critical 9.3)
- [CVE-2026-25635](https://insights.sbomify.com/CVE-2026-25635/): calibre has a Path Traversal Leading to Arbitrary File Write and Potential Code Execution (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-25731 and fix it if it is affected.

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

Affected product: kovidgoyal calibre. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-25731/ (Markdown: https://insights.sbomify.com/CVE-2026-25731/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-25731
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-25731
- OSV: https://osv.dev/vulnerability/CVE-2026-25731

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-25731/
Summaries are generated and may contain mistakes; the official description above is the record.