CVE-2024-1135: HTTP Request Smuggling in benoitc/gunicorn

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 3.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-04-16 · updated 2026-06-17
Weakness: CWE-444

Description

Gunicorn fails to properly validate Transfer-Encoding headers, leading to HTTP Request Smuggling (HRS) vulnerabilities. By crafting requests with conflicting Transfer-Encoding headers, attackers can bypass security restrictions and access restricted endpoints. This issue is due to Gunicorn's handling of Transfer-Encoding headers, where it incorrectly processes requests with multiple, conflicting Transfer-Encoding headers, treating them as chunked regardless of the final encoding specified. This vulnerability allows for a range of attacks including cache poisoning, session manipulation, and data exposure.

Affected products

benoitc Gunicorn: all versions
Pypi Gunicorn: before 22.0.0; 0.1, 0.10.0, 0.10.1, 0.11.0, 0.11.1, 0.11.2 (+79) — fixed in 22.0.0

How to fix

Upgrade to a fixed version: Pypi Gunicorn 22.0.0. Check the vendor advisory for mitigations.

References

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