CVE-2021-3874 Details
A vulnerability, which was classified as critical, was found in BookStack (version unknown). Affected is an unknown code block. Applying the patch 7224fbcc89f00f2b71644e36bb1b1d96addd1d5a is able to eliminate this problem. The bugfix is ready for download at github.com.
View at NVD
Exploit prediction scoring system (EPSS) score for CVE-2021-3874
EPSS (Exploit Prediction Scoring System): EPSS predicts the likelihood that a vulnerability will be exploited in the wild. A higher percentage means a greater chance of an exploit occurring. The EPSS model produces a probability score between 0 and 1 (0 and 100%).
0.38 Probability of exploitation activity being observed over the next 30 days (59th percentile)
CVSS score for CVE-2021-3874
CVSS (Common Vulnerability Scoring System): An open framework owned and managed by FIRST.Org, Inc. that assigns a numerical score from 0 to 10 to software vulnerabilities to indicate their severity.
6.5 Medium
Products affected by CVE-2021-3874
Bookstack 0.21.0
Bookstack 0.23.2
Bookstack 0.25.2
Bookstack 0.26.2
Bookstack 0.29.3
DVE Score by Bitsight AI
DVE scores complement traditional static scoring systems like CVSS with Bitsight AI powered real-time threat intelligence and underground cyber criminal activity so that security teams can reduce alert fatigue and focus on vulnerabilities most likely to be exploited.
Not available
More on DVE scores

CVE-2021-3874 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
US 22 36.07%
DE 15 24.59%
RU 6 9.84%
FR 4 6.56%
BR 3 4.92%
PL 3 4.92%
GB 2 3.28%
CA 1 1.64%
EE 1 1.64%
FI 1 1.64%

Is CVE-2021-3874 part of your extended attack surface? Bitsight helps security leaders rapidly identify exposure and detect threats in order to prioritize, communicate, and mitigate risk.

View interactive product tours

CVE-2021-3874 Industry Footprint

Top 10 Identified Industries

*Service provider organizations (typically Technology and Telecommunications) are disproportionally represented in the results given their upstream ownership of end-user infrastructure. See our FAQs.

Industry* Observations Percentage
Technology 50 98.04%
Government/Politics 1 1.96%

Bitsight Data Discovery and Continuous Threat Scanning

Bitsight, the leading provider in Cyber Risk Management, introduced the next-generation internet scanner Bitsight Groma in May 2024. This technology continuously scans the entire internet to discover assets, collect asset attribution evidence, and identify an ever-growing set of security observations, such as vulnerabilities and misconfigurations. Groma’s scanning activities presently encompass:


  • 40 million-plus monitored organizations
  • 250 million-plus host names
  • 4 billion-plus routable IPv4 and IPv6 addresses

Greynoise’s recent study testifies the speed of Bitsight Groma.

Learn more about Bitsight Groma
Bitsight data discovery
Governance charcoal background

How we use Bitsight Groma data 

Empower Security Research

Bitsight TRACE team investigates security incidents and identifies vulnerabilities and threats.

View latest security research 

See Your External Attack Surface

See what you’re up against across the expanding attack surface. Prioritize what matters most. And mitigate where you’re most vulnerable.

External Attack Surface Management

Bitsight ASA Report Image

Your attack surface is expanding—know exactly how it looks

Reducing exposure starts with knowing exactly how your external attack surface stands—from your overall standing to each digital and cloud asset around the world. Bitsight's custom report gives you the insights you need to see your entire external attack surface.

Get a free attack surface report