flatnotes 5.5.4 Attachment Handling unrestricted upload

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.1$0-$5k0.00

Summaryinfo

A vulnerability identified as critical has been detected in flatnotes 5.5.4. Affected is an unknown function of the component Attachment Handling. Performing a manipulation results in unrestricted upload. This vulnerability is known as CVE-2026-50873. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability classified as critical has been found in flatnotes 5.5.4. This affects some unknown functionality of the component Attachment Handling. The manipulation with an unknown input leads to a unrestricted upload vulnerability. CWE is classifying the issue as CWE-434. The product allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

An arbitrary file upload vulnerability in the attachment handling component of flatnotes v5.5.4 allows attackers to execute arbitrary code via uploading a crafted HTML or SVG file.

The advisory is shared at gist.github.com. This vulnerability is uniquely identified as CVE-2026-50873 since 06/07/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/16/2026). MITRE ATT&CK project uses the attack technique T1608.002 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.3
VulDB Meta Temp Score: 6.1

VulDB Base Score: 6.3
VulDB Temp Score: 6.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Unrestricted upload
CWE: CWE-434 / CWE-284 / CWE-266
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

06/07/2026 CVE reserved
06/16/2026 +9 days Advisory disclosed
06/16/2026 +0 days VulDB entry created
06/16/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: gist.github.com
Status: Not defined

CVE: CVE-2026-50873 (🔒)
GCVE (CVE): GCVE-0-2026-50873
GCVE (VulDB): GCVE-100-371205

Entryinfo

Created: 06/16/2026 07:00
Changes: 06/16/2026 07:00 (52)
Complete: 🔍
Cache ID: 216::103

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