# CVE-2021-3986: PYSEC-2026-1232 - Generation of Error Message Containing Sensitive Information in janeczku/calibre-web

Source: https://junglewise.ai/threats/cve-2021-3986-generation-of-error-message-containing-sensitive-information-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-07  
License: CC BY 4.0 with a link back

CVE-2021-3986 · Severity: low · CVSS 3.1 · Published 2026-07-07

Generation of Error Message Containing Sensitive Information in janeczku/calibre-web

Technologies: [calibreweb (PyPI)](https://junglewise.ai/threats/technologies/calibreweb). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-3986 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-3986 being exploited in the wild.

**How severe is CVE-2021-3986?** Low severity, with a CVSS score of 3.1, published 7 July 2026.

**Which products and versions are affected?** calibreweb (PyPI) ECOSYSTEM:introduced=0,fixed=0.6.15.

**Is there a fix for CVE-2021-3986?** Yes. calibreweb (PyPI): upgrade to 0.6.15 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-3986?** Check whether you run calibreweb (PyPI) 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.

## How to fix

- calibreweb (PyPI): upgrade to 0.6.15 or later

  ```sh
  pip install "calibreweb>=0.6.15"
  ```


## Affected products

- calibreweb (PyPI) ECOSYSTEM:introduced=0,fixed=0.6.15

## Identifiers

- CVE-2021-3986
- GHSA-m982-h4f8-g4hf
- PYSEC-2026-1232

## Related threats

- [PYSEC-2026-1228 - Calibre Web and Autocaliweb have a ReDoS vulnerability](https://junglewise.ai/threats/cve-2025-6998-calibre-web-and-autocaliweb-redos-in-strip-whitespaces)
- [PYSEC-2026-1235 - Calibre Web and Autocaliweb have OS Command Injection vulnerability](https://junglewise.ai/threats/cve-2025-7404-calibre-web-and-autocaliweb-have-os-command-injection)
- [PYSEC-2026-1236 - Cross-site Scripting (XSS) - DOM in janeczku/calibre-web](https://junglewise.ai/threats/cve-2021-3988-cross-site-scripting-xss-dom-in-janeczku-calibre-web)
- [PYSEC-2026-1229 - Improper Access Control in janeczku/calibre-web](https://junglewise.ai/threats/cve-2021-3987-improper-access-control-in-janeczku-calibre-web)
- [PYSEC-2026-1230 - Calibre-Web Cross Site Scripting (XSS)](https://junglewise.ai/threats/cve-2024-39123-calibre-web-cross-site-scripting-xss)