CVE-2021-3988 json
Cross-site Scripting (XSS) in janeczku/calibre-web
published last yr. modified 4mo ago also GHSA-r735-9gc6-2hvq , PYSEC-2026-1236 , EUVD-2024-3306
- cvss
- 5.7
- version 3.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 32%
- public exploits
- 0
- none known
Summary
A Cross-site Scripting (XSS) vulnerability exists in janeczku/calibre-web, specifically in the file `edit_books.js`. The vulnerability occurs when editing book properties, such as uploading a cover or a format. The affected code directly inserts user input into the DOM without proper sanitization, allowing attackers to execute arbitrary JavaScript code. This can lead to various attacks, including stealing cookies. The issue is present in the code handling the `#btn-upload-cover` change event.
Patch / fix
Is CVE-2021-3988 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- no
- Technical impact
- partial
- Assessed
- last yr.
Exploit prediction
0.38% chance of exploitation in the next 30 days, higher than 32% of all scored CVEs (FIRST EPSS, 2026-11-09).
Exploits and checks
- huntr.com https://huntr.com/bounties/fa4c8fd1-7846-4dad-9112-2c07461f0609 referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.0 | 5.7 | CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N |
| NVD | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
| OSV | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
| GitHub | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | calibreweb | <0.6.15 |
0.6.15 |
Affected products
- janeczku janeczku/calibre-web
- janeczku calibre-web
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
-
github.com
/janeczku/calibre-web/commit/7ad419dc8c12180e842a82118f4866ac3d074bc5
web, patch
-
huntr.com
/bounties/fa4c8fd1-7846-4dad-9112-2c07461f0609
web, exploit
-
nvd.nist.gov
/vuln/detail/CVE-2021-3988
advisory
-
github.com
/janeczku/calibre-web
package
-
pypi.org
/project/calibreweb
package
-
github.com
/advisories/GHSA-r735-9gc6-2hvq
advisory
Sources
- CVE List CVE-2021-3988
- GitHub Advisory GHSA-r735-9gc6-2hvq
- NVD CVE-2021-3988
- OSV PYSEC-2026-1236
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.