How severe is CVE-2021-3915?

CVE-2021-3915 has a CVSS 3.x base score of 5.7, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-3915 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3915?

CVE-2021-3915 affects Bookstackapp Bookstack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3915?

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

When was CVE-2021-3915 published?

CVE-2021-3915 was published on 2021-11-13 and last updated on 2026-06-17.

CVE-2021-3915

CVE-2021-3915 is a medium-severity vulnerability in Bookstackapp Bookstack with a CVSS 3.x base score of 5.7. 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-434.

Key facts

Severity: Medium (CVSS 3.x base score 5.7)
CVSS v2: 3.5
EPSS exploit prediction: 1% (56th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-434
Affected product: Bookstackapp Bookstack
Published: 2021-11-13
Last modified: 2026-06-17

Description

bookstack is vulnerable to Unrestricted Upload of File with Dangerous Type

Frequently asked questions

What is CVE-2021-3915?: bookstack is vulnerable to Unrestricted Upload of File with Dangerous Type
How severe is CVE-2021-3915?: CVE-2021-3915 has a CVSS 3.x base score of 5.7, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-3915 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (56th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3915?: CVE-2021-3915 affects Bookstackapp Bookstack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3915?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-3915 published?: CVE-2021-3915 was published on 2021-11-13 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…

All CVEs affecting Bookstackapp Bookstack →

Other CWE-434 (Unrestricted Upload of File with Dangerous Type) vulnerabilities

CVE-2026-48283 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Unrestricted Upload of File with Dangerous Type…
CVE-2026-48276 — Critical (CVSS 10.0): ColdFusion versions 2025.9, 2023.20 and earlier are affected by an Unrestricted Upload of File with Dangerous Type…
CVE-2026-57700 — Critical (CVSS 10.0): Unrestricted Upload of File with Dangerous Type vulnerability in Daan.Dev OMGF Pro allows Using Malicious Files. This…
CVE-2025-69129 — Critical (CVSS 10.0): Unauthenticated Arbitrary File Upload in WordPress & WooCommerce Scraper Plugin, Import Data from Any Site <= 1.0.7…
CVE-2026-40772 — Critical (CVSS 10.0): Unauthenticated Arbitrary File Upload in GeekyBot <= 1.2.2 versions.
CVE-2026-40412 — Critical (CVSS 10.0): Unrestricted upload of file with dangerous type in Azure Orbital Spatio allows an unauthorized attacker to execute code…

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