CVE-2021-3874Public exploitNetwork attack vector

Authenticated file disclosure via export path traversal

Published Oct 15, 2021 · Updated Aug 3, 2024

Path traversal in BookStack before 21.08.5 allows remote authenticated users to read server files through HTML page exports. AttachmentService and ImageService accepted traversal segments in content-referenced paths while using storage filesystems rooted above the intended upload directories. Exploitation requires permission to create or update pages and exposes readable files under the storage or public directories, including application logs.

CVSS severity6.5
Medium
EPSS probability1.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Path traversal in BookStack before 21.08.5 allows remote authenticated users to read server files through HTML page exports. AttachmentService and ImageService accepted traversal segments in content-referenced paths while using storage filesystems rooted above the intended upload directories. Exploitation requires permission to create or update pages and exposes readable files under the storage or public directories, including application logs.

The record

CVE
CVE-2021-3874
Published
Oct 15, 2021
Updated
Aug 3, 2024
Vendor
BookStack
Product
BookStack
Classifications
CWE-22, T1005
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <21.08.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

BookStack · BookStackversion=unspecified <21.08.5

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:P/I:N/A:N
4.3huntr.devCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1005Data from Local System

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo