CVE-2025-61773

pyLoad web interface contained insufficient input validation in both the Captcha script endpoint and the Click'N'Load (CNL) Blueprint. This flaw allowed untrusted user input to be processed unsafely, which could be exploited by an attacker to inject arbitrary content into the web UI or manipulate request handling. The vulnerability could lead to client-side code execution (XSS) or other unintended behaviors when a malicious payload is submitted.

user-supplied parameters from HTTP requests were not adequately validated or sanitized before being passed into the application logic and response generation. This allowed crafted input to alter the expected execution flow.
CNL (Click'N'Load) blueprint exposed unsafe handling of untrusted parameters in HTTP requests. The application did not consistently enforce input validation or encoding, making it possible for an attacker to craft malicious requests.

PoC

1. Run a vulnerable version of pyLoad prior to commit f9d27f2.
2. Start the web UI and access the Captcha or CNL endpoints.
3. Submit a crafted request containing malicious JavaScript payloads in unvalidated parameters (/flash/addcrypted2?jk=function(){alert(1)}&crypted=12345).
4. Observe that the payload is reflected and executed in the client’s browser, demonstrating cross-site scripting (XSS).

Example request:

GET /flash/addcrypted2?jk=function(){alert(1)}&crypted=12345 HTTP/1.1
Host: 127.0.0.1:8000
Content-Type: application/x-www-form-urlencoded
Content-Length: 107

Refferences

• https://github.com/pyload/pyload/commit/5823327d0b797161c7195a1f660266d30a69f0ca
• @4624

Exploiting this vulnerability allows an attacker to inject and execute arbitrary JavaScript within the browser session of a user accessing the pyLoad Web UI. In practice, this means an attacker could impersonate an administrator, steal authentication cookies or tokens, and perform unauthorized actions on behalf of the victim. Because the affected endpoints are part of the core interface, a successful attack undermines the trust and security of the entire application, potentially leading to a full compromise of the management interface and the data it controls. The impact is particularly severe in cases where the Web UI is exposed over a network without additional access restrictions, as it enables remote attackers to directly target users with crafted links or requests that trigger the vulnerability.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2025-61773 has a CVSS score of 8.1 (High). The vector is network-reachable, no privileges required, and user interaction required. 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 (0.5.0b3.dev91); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-61773? CVE-2025-61773 is a high-severity cross-site scripting (XSS) vulnerability in pyload-ng (pip), affecting versions < 0.5.0b3.dev91. It is fixed in 0.5.0b3.dev91. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2025-61773? CVE-2025-61773 has a CVSS score of 8.1 (High). 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.
3. Which versions of pyload-ng are affected by CVE-2025-61773? pyload-ng (pip) versions < 0.5.0b3.dev91 is affected.
4. Is there a fix for CVE-2025-61773? Yes. CVE-2025-61773 is fixed in 0.5.0b3.dev91. Upgrade to this version or later.
5. Is CVE-2025-61773 exploitable, and should I be worried? Whether CVE-2025-61773 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
6. What actually determines whether CVE-2025-61773 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.
7. How do I fix CVE-2025-61773? Upgrade pyload-ng to 0.5.0b3.dev91 or later.

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