CVE-2025-61773 is a high-severity (CVSS 8.1) remote code execution vulnerability in pyload-ng. A fix is available for pyload-ng — see the affected versions and patch details below.
pyLoad CNL and captcha handlers allow code Injection via unsanitized parameters
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-61773.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-61773 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
pyload-ngReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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
- Run a vulnerable version of pyLoad prior to commit
f9d27f2. - Start the web UI and access the Captcha or CNL endpoints.
- Submit a crafted request containing malicious JavaScript payloads in unvalidated parameters (
/flash/addcrypted2?jk=function(){alert(1)}&crypted=12345). - 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
Impact
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyload-ng | all versions | 0.5.0b3.dev91pip install --upgrade 'pyload-ng==0.5.0b3.dev91' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyload-ng, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyload-ng to 0.5.0b3.dev91 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-61773 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-61773 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-61773. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-61773 in your dependencies?
O3 Security finds CVE-2025-61773 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.