CVE-2026-40594: pyLoad is a free and open-source download manager written in Python. Prior to 0.5.0b3.dev98, the set_session_cookie_secure before_request handler in s...

Description

pyLoad is a free and open-source download manager written in Python. Prior to 0.5.0b3.dev98, the set_session_cookie_secure before_request handler in src/pyload/webui/app/__init__.py reads the X-Forwarded-Proto header from any HTTP request without validating that the request originates from a trusted proxy, then mutates the global Flask configuration SESSION_COOKIE_SECURE on every request. Because pyLoad uses the multi-threaded Cheroot WSGI server (request_queue_size=512), this creates a race condition where an attacker's request can influence the Secure flag on other users' session cookies — either downgrading cookie security behind a TLS proxy or causing a session denial-of-service on plain HTTP deployments. This vulnerability is fixed in 0.5.0b3.dev98.

Metrics

CVSS 3.1

4.8/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

EPSS Probability

0.17%

6.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-346

Affected Software

Vendor	Product	Versions
Pyload-Ng Project	Pyload-Ng	< 0.5.0b3.dev69

References

https://github.com/pyload/pyload/security/advisories/GHSA-mp82-fmj6-f22vExploit, Mitigation, Vendor Advisory
https://github.com/pyload/pyload/security/advisories/GHSA-mp82-fmj6-f22vExploit, Mitigation, Vendor Advisory

Timeline

Published: Apr 21, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-40594?

pyLoad is a free and open-source download manager written in Python. Prior to 0.5.0b3.dev98, the set_session_cookie_secure before_request handler in src/pyload/webui/app/__init__.py reads the X-Forwarded-Proto header from any HTTP request without validating that the request originates from a trusted proxy, then mutates the global Flask configuration SESSION_COOKIE_SECURE on every request. Because pyLoad uses the multi-threaded Cheroot WSGI server (request_queue_size=512), this creates a race condition where an attacker's request can influence the Secure flag on other users' session cookies — either downgrading cookie security behind a TLS proxy or causing a session denial-of-service on plain HTTP deployments. This vulnerability is fixed in 0.5.0b3.dev98.

How severe is CVE-2026-40594?

CVE-2026-40594 has a CVSS score of 4.8/10 (MEDIUM severity). The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-40594?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

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