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Advisory details: pypa / pyload-ng/PYSEC-2026-1816
Advisory ID pypa/pyload-ng/PYSEC-2026-1816
Aliases CVE-2025-61773
GHSA-cjjf-27cc-pvmv
PYSEC-2026-1816
Summary pyLoad CNL and captcha handlers allow Code Injection via unsanitized parameters ### 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 1. Run a vulnerable version of pyLoad prior to commit [`f9d27f2`](https://github.com/pyload/pyload/pull/4624). 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: ```http 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`](https://github.com/pyload/pyload/pull/4624) ### 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.
Status Published
Exploitability 0.5
Weighted Severity 7.3
Risk 3.6
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (0)
There are no known CWE.
System Score Found at
cvssv3.1 8.1 https://github.com/pypa/advisory-database/blob/main/vulns/pyload-ng/PYSEC-2026-1816.yaml
Reference id Reference type URL
https://github.com/pyload/pyload
https://github.com/pyload/pyload/commit/5823327d0b797161c7195a1f660266d30a69f0ca
https://github.com/pyload/pyload/pull/4624
https://pypi.org/project/pyload-ng
CVE-2025-61773 https://nvd.nist.gov/vuln/detail/CVE-2025-61773
GHSA-cjjf-27cc-pvmv https://github.com/advisories/GHSA-cjjf-27cc-pvmv
GHSA-cjjf-27cc-pvmv https://github.com/pyload/pyload/security/advisories/GHSA-cjjf-27cc-pvmv
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://github.com/pypa/advisory-database/blob/main/vulns/pyload-ng/PYSEC-2026-1816.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2025-10-10T14:29:28Z/

Decision: Track*

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2025/61xxx/CVE-2025-61773.json

Source Advisory: vulnrichment/CVE-2025-61773

View SSVC decision tree 
[{'Exploitation': 'poc'},
 {'Automatable': 'no'},
 {'Technical Impact': 'total'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]