CVE-2020-5256
HIGHEPSS 78th pctlDescription
BookStack before version 0.25.5 has a vulnerability where a user could upload PHP files through image upload functions, which would allow them to execute code on the host system remotely. They would then have the permissions of the PHP process. This most impacts scenarios where non-trusted users are given permission to upload images in any area of the application. The issue was addressed in a series of patches in versions 0.25.3, 0.25.4 and 0.25.5. Users should upgrade to at least v0.25.5 to avoid this vulnerability.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:L
Exploit Intelligence
Elevated risk: more likely to be exploited than 78% of all known CVEs.
References
Related Vulnerabilities
Other CWE-95 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-24893 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2026-33017 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2024-36401 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2024-21650 | Critical | 10.0 | 93% | - | - |
| CVE-2023-37462 | Critical | 9.9 | 91% | - | Fix |
| CVE-2024-7954 | Critical | 9.8 | 90% | - | Fix |
Common questions
How do I fix CVE-2020-5256?
Upgrade bookstack to 0.25.3 or later.
Is CVE-2020-5256 being actively exploited?
Not that we know of. CVE-2020-5256 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 2.0% is the estimated probability that it will be exploited in the next 30 days. That is higher than 78% of all scored CVEs.
How severe is CVE-2020-5256?
CVE-2020-5256 has a CVSS v3 base score of 7.9, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2020-5256 affect?
Published advisories record a fix for bookstack (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.