What is CVE-2021-4119?

CVE-2021-4119 is a critical-severity vulnerability in Bookstackapp Bookstack, classified under Improper Access Control. CVSS score: 9.8/10. Published 2021-12-15.

How severe is CVE-2021-4119?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2021-4119 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Bookstackapp Bookstack

CVE-2021-4119

bookstack is vulnerable to Improper Access Control

Published 2021-12-15 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.269 (98.0th percentile), scored 2026-09-28.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 98th percentile — 98.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.269 · newest: 0.269 · change: 0.000

Affected products

Bookstackapp Bookstack
Bookstackapp Bookstackapp/bookstack — versions unspecified

Weakness classification (CWE)

CWE-284 — Improper Access Control

Public proof-of-concept exploits

References

huntr.dev/bounties/135f2d7d-ab0b-4351-99b9-889efac46fca (Exploit, Patch, Third Party Advisory)
github.com/bookstackapp/bookstack/commit/e765e618547c92f4e0b46caca6fb91f0174efd… (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-4119?: CVE-2021-4119 is a critical-severity vulnerability in Bookstackapp Bookstack, classified under Improper Access Control. CVSS score: 9.8/10. Published 2021-12-15.
How severe is CVE-2021-4119?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-4119 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.