How severe is CVE-2021-3874?

CVE-2021-3874 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-3874 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3874?

CVE-2021-3874 affects Bookstackapp Bookstack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3874?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-3874 published?

CVE-2021-3874 was published on 2021-10-15 and last updated on 2026-06-17.

CVE-2021-3874

CVE-2021-3874 is a medium-severity vulnerability in Bookstackapp Bookstack with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.0
EPSS exploit prediction: 1% (63rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-22
Affected product: Bookstackapp Bookstack
Published: 2021-10-15
Last modified: 2026-06-17

Description

bookstack is vulnerable to Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Frequently asked questions

What is CVE-2021-3874?: bookstack is vulnerable to Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
How severe is CVE-2021-3874?: CVE-2021-3874 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-3874 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3874?: CVE-2021-3874 affects Bookstackapp Bookstack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3874?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3874 published?: CVE-2021-3874 was published on 2021-10-15 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:bookstackapp:bookstack:*:*:*:*:*:*:*:*

More vulnerabilities in Bookstackapp Bookstack

CVE-2021-4119 — Critical (CVSS 9.8): bookstack is vulnerable to Improper Access Control
CVE-2020-5256 — High (CVSS 7.9): BookStack before version 0.25.5 has a vulnerability where a user could upload PHP files through image upload functions,…
CVE-2020-26211 — High (CVSS 7.7): In BookStack before version 0.30.4, a user with permissions to edit a page could insert JavaScript code through the use…
CVE-2020-26210 — High (CVSS 7.7): In BookStack before version 0.30.4, a user with permissions to edit a page could add an attached link which would…
CVE-2021-3944 — Medium (CVSS 6.8): bookstack is vulnerable to Cross-Site Request Forgery (CSRF)
CVE-2023-6199 — Medium (CVSS 6.5): Book Stack version 23.10.2 allows filtering local files on the server. This is possible because the application is…

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Other CWE-22 (Path Traversal) vulnerabilities

CVE-2026-48282 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Improper Limitation of a Pathname to a Restricted…
CVE-2026-54917 — Critical (CVSS 10.0): SeaweedFS is a distributed storage system for object storage (S3), file systems, and Iceberg tables. Prior to 4.30, the…
CVE-2026-11429 — Critical (CVSS 10.0): Two endpoints in the Vault Service ScriptsController, shared by Altium Enterprise Server and Altium 365, accept file…
CVE-2026-34909 — Critical (CVSS 10.0): A malicious actor with access to the network could exploit a Path Traversal vulnerability found in UniFi OS devices to…
CVE-2026-7411 — Critical (CVSS 10.0): In Eclipse BaSyx Java Server SDK versions prior to 2.0.0-milestone-10, inadequate path normalization in the Submodel…
CVE-2026-36767 — Critical (CVSS 10.0): A path traversal vulnerability in the /content/images/add endpoint of shopizer v3.2.5 allows attackers write arbitrary…

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