CVE-2021-3987: An improper access control vulnerability exists in janeczku/calibre-web

Q: How do I fix CVE-2021-3987?

calibre-web: upgrade to 0.6.15. Exact commands for each OS are on this page.

Q: Is CVE-2021-3987 being exploited?

CVE-2021-3987 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-3987 affect?

CVE-2021-3987 affects calibre-web. Severity is medium (CVSS 4.3). An improper access control vulnerability exists in janeczku/calibre-web. The affected version allows users without public shelf permissions to create public shelves. The vulnerability is due to the `create_shelf` method in `shelf.py` not ve

Q: How urgent is CVE-2021-3987?

Priority 27/100. Public exploit reference

Routine

MEDIUM 4.3UPGRADE

CVE-2021-3987 is a medium-severity flaw (CVSS 4.3) affecting calibre-web. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An improper access control vulnerability exists in janeczku/calibre-web. The affected version allows users without public shelf permissions to create public shelves. The vulnerability is due to the `create_shelf` method in `shelf.py` not verifying if the user has the necessary permissions to create a public shelf. This issue can lead to unauthorized actions being performed by users.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 72%)
CISA exploited list	No
Weakness	CWE-284, CWE-862
Published	2024-11-15
Last modified	2026-06-17

Publisher (CNA): huntr.dev · Vendor: janeczku

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2024-11-15 11:15 UTCPublished CVE record published
2026-06-17 04:06 UTCUpdated Record last modified

janeczku calibre-web UPGRADE

Affected: < 0.6.15

Fixed in: 0.6.15

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy calibre-web || rpm -q calibre-web || calibre-web --version

2. UPGRADE to 0.6.15 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade calibre-web

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade calibre-web

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-3987?

calibre-web: upgrade to 0.6.15. Exact commands for each OS are on this page.

Is CVE-2021-3987 being exploited?

CVE-2021-3987 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-3987 affect?

CVE-2021-3987 affects calibre-web. Severity is medium (CVSS 4.3). An improper access control vulnerability exists in janeczku/calibre-web. The affected version allows users without public shelf permissions to create public shelves. The vulnerability is due to the `create_shelf` method in `shelf.py` not ve

How urgent is CVE-2021-3987?

Priority 27/100. Public exploit reference

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References

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