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Hedgedoc CVE-2020-26286

HIGH
Unrestricted Upload of File with Dangerous Type (CWE-434)
2020-12-29 security-advisories@github.com
7.5
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V5 - File Handling File type validation, storage isolation
MITRE ATT&CK

2 techniques across 2 tactics: Command and Control, Persistence

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required.

Exploit ScenarioDerived

A remote attacker could upload malicious files that can be executed on the server by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 1.4% exploitation probability (EPSS)

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AnalysisAI

HedgeDoc is a collaborative platform for writing and sharing markdown. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Unrestricted File Upload vulnerability could allow attackers to upload malicious files that can be executed on the server.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Validate file types server-side, store uploads outside webroot, use random filenames, scan for malware.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Unrestricted File Upload (CWE-434), which allows attackers to upload malicious files that can be executed on the server. HedgeDoc is a collaborative platform for writing and sharing markdown. In HedgeDoc before version 1.7.1 an unauthenticated attacker can upload arbitrary files to the upload storage backend including HTML, JS and PHP files. The problem is patched in HedgeDoc 1.7.1. You should however verify that your uploaded file storage only contains files that are allowed, as uploaded files might still be served. As workaround it's possible to block the /uploadimage endpoint on your instance using your reverse proxy. And/or restrict MIME-types and file names served from your upload file storage. Affected products include: Hedgedoc. Version information: version 1.7.1.

Severity by source

NVD PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

DescriptionNVD

HedgeDoc is a collaborative platform for writing and sharing markdown. In HedgeDoc before version 1.7.1 an unauthenticated attacker can upload arbitrary files to the upload storage backend including HTML, JS and PHP files. The problem is patched in HedgeDoc 1.7.1. You should however verify that your uploaded file storage only contains files that are allowed, as uploaded files might still be served. As workaround it's possible to block the /uploadimage endpoint on your instance using your reverse proxy. And/or restrict MIME-types and file names served from your upload file storage.

Threat Intelligence Overview

EPSS Score
1.4%
Top 30% exploitable
Data Quality
3 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 1.4%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
None
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
Medium

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Malicious file upload attacks exploit insufficient validation when web applications accept user-provided files.

Affected Products (CPE)NVD

cpe:2.3:a:hedgedoc:hedgedoc:*:*:*:*:*:*:*:*
CVE-2020-26287 HIGH POC
8.7 Dec 29

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CVE-2023-38487 HIGH POC
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CVE-2024-45308 MEDIUM POC
6.5 Sep 02

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CVE-2021-21259 MEDIUM POC
6.1 Jan 22

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CVE-2021-29475 CRITICAL
10.0 Apr 26

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CVE-2021-29474 MEDIUM POC
5.8 Apr 26

HedgeDoc (formerly known as CodiMD) is an open-source collaborative markdown editor. Rated medium severity (CVSS 5.8), t

CVE-2026-58486 HIGH
8.3 Jul 13

Denial of service in HedgeDoc before 1.11.0 lets a user who can store a note crash the instance by embedding a YAML "ali

CVE-2026-58488 MEDIUM
6.9 Jul 13

Rate-limiting bypass in HedgeDoc prior to 1.11.0 permits unauthenticated remote attackers to circumvent brute-force prot

CVE-2026-58489 MEDIUM
6.8 Jul 13

HedgeDoc's GitHub Gist export feature exposes private and protected note content to attacker-controlled GitHub accounts

CVE-2025-32391 MEDIUM POC
6.4 Apr 10

HedgeDoc is an open source, real-time, collaborative, markdown notes application. Rated medium severity (CVSS 6.4), this

CVE-2021-39175 MEDIUM
6.1 Aug 30

HedgeDoc is a platform to write and share markdown. Rated medium severity (CVSS 6.1), this vulnerability is remotely exp

CVE-2021-29503 MEDIUM
6.1 May 19

HedgeDoc is a platform to write and share markdown. Rated medium severity (CVSS 6.1), this vulnerability is remotely exp

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