CVE-2026-43939

YAF.NET: Stored XSS in Forum Thread Posts/Replies Allowing Arbitrary JavaScript Execution for All Thread Viewers

HIGH
7.3
CVSS Score
Published: May 12, 2026 at 01:56 PM UTC
Updated: June 17, 2026 at 10:50 AM UTC
1 product affected across 1 vendorYAFNET

Using YAFNET by YAFNET?

Get instant alerts when new vulnerabilities affect YAFNET - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Severity
HIGH7.3
Exploit prediction
EPSS 0.2%
SSVC
PoC

Description

YetAnotherForum.NET (YAF.NET) is a C# ASP.NET forum. Prior to 4.0.5 and 3.2.12, the thread posting and reply feature accepts user-supplied content via a a post or reply that is stored server-side and later rendered back into the thread page without adequate HTML sanitization or contextual output encoding. This vulnerability is fixed in 4.0.5 and 3.2.12.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 3.2.12v < 4.0.5
Affected range stops below 3.2.12, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.0.5, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (1)

SSVC — Action Prioritization

SSVCPoCNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.3HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79CWE-80CWE-116

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Free plan, no card