pyLoad: Rate-Limit Bypass and Audit-Log Spoofing via Trusted Client-Controlled X-Forwarded-For Header

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary pyLoad determines the "client IP" used for its rate-limiting decorator and for its security/audit logging by reading the client-supplied X-Forwarded-For (XFF) HTTP header and taking the leftmost value. No trusted-proxy configuration exists (the Cheroot WSGI server faces clients directly, and there is no ProxyFix middleware). Because any client can freely set this header, an attacker can (1) completely bypass rate limiting by rotating the header on each request, and (2) forge the source IP recorded in security logs for login and API-key authentication failures, defeating IP-based blocking (e.g. fail2ban) and poisoning attribution. Severity Medium — CVSS 3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L (~5.3) - CWE-807: Reliance on Untrusted Inputs in a Security Decision - CWE-290: Authentication Bypass by Spoofing - CWE-348: Use of Less Trusted Source Affected Version pyLoad 0.5.0b3 (built from the develop branch). Confirmed still present and exploitable in the later pyload-develop-2…

Published by the source

9 Oct 2026, 17:09 UTC

Last modified by the source

9 Oct 2026, 17:09 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-9q47-3cm2-2rp8

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# Patch Next advisory brief: GHSA-9q47-3cm2-2rp8

Advisory: pyLoad: Rate-Limit Bypass and Audit-Log Spoofing via Trusted Client-Controlled `X-Forwarded-For` Header
IDs: GHSA-9q47-3cm2-2rp8
Record: https://patchnext.com/advisories/ghsa-9q47-3cm2-2rp8 (revision 1, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI pyload-ng: affected >= 0.5.0b3.dev101, <= 0.5.0b3.dev101

## Suggested inspection (read-only)
- `python -m pip show pyload-ng`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pyload-ng.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-9q47-3cm2-2rp8 (GitHub-reviewed advisory GHSA-9q47-3cm2-2rp8 lists affected ranges: PyPI pyload-ng >=0.5.0b3.dev101 <=0.5.0b3.dev101)

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