Inconsistent interpretation of HTTP requests in Traefik - CVE-2021-32813
Published: August 3, 2021 / Updated: May 5, 2026
Vulnerability identifier: #VU129660
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: CVE-2021-32813
CWE-ID: CWE-444
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Containous
Affected software:
Traefik
Traefik
Detailed vulnerability description
The vulnerability allows a remote attacker to remove security-relevant request headers.
The vulnerability exists due to improper handling of hop-by-hop headers in Connection header processing when handling crafted HTTP requests through a chain of middlewares. A remote attacker can send a specially crafted request with a malicious Connection header to remove security-relevant request headers.
This can occur when one middleware sets a request header that is later stripped before the request is forwarded to the backend.
How to mitigate CVE-2021-32813
Install security update from vendor's website.