How severe is CVE-2020-26210?

CVE-2020-26210 has a CVSS 3.x base score of 7.7, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2020-26210 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-2020-26210?

CVE-2020-26210 affects Bookstackapp Bookstack. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-26210?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-26210 published?

CVE-2020-26210 was published on 2020-11-03 and last updated on 2026-06-17.

CVE-2020-26210

CVE-2020-26210 is a high-severity vulnerability in Bookstackapp Bookstack with a CVSS 3.x base score of 7.7. 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-79.

Key facts

Severity: High (CVSS 3.x base score 7.7)
CVSS v2: 3.5
EPSS exploit prediction: 1% (63rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Bookstackapp Bookstack
Published: 2020-11-03
Last modified: 2026-06-17

Description

In BookStack before version 0.30.4, a user with permissions to edit a page could add an attached link which would execute untrusted JavaScript code when clicked by a viewer of the page. Dangerous content may remain in the database after this update. If you think this could have been exploited the linked advisory provides a SQL query to test. As a workaround, page edit permissions could be limited to only those that are trusted until you can upgrade although this will not address existing exploitation of this vulnerability. The issue is fixed in version 0.30.4.

Frequently asked questions

What is CVE-2020-26210?: In BookStack before version 0.30.4, a user with permissions to edit a page could add an attached link which would execute untrusted JavaScript code when clicked by a viewer of the page. Dangerous content may remain in the database after this update. If you think this could have been exploited the linked advisory provides a SQL query to test. As a workaround, page edit permissions could be limited to only those that are trusted until you can upgrade although this will not address existing exploitation of this vulnerability. The issue is fixed in version 0.30.4.
How severe is CVE-2020-26210?: CVE-2020-26210 has a CVSS 3.x base score of 7.7, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2020-26210 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-2020-26210?: CVE-2020-26210 affects Bookstackapp Bookstack. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-26210?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-26210 published?: CVE-2020-26210 was published on 2020-11-03 and last updated on 2026-06-17.

References

Affected products (1)

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

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