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Fencer Vulns
medium 4.8

CVE-2021-32813 json

Drop Headers via Malicious Connection Header

published 2021-08-03 5 y ago modified 2026-07-08 4 mo ago also GHSA-m697-4v8f-55qg , GO-2022-0923 , EUVD-2021-1790

cvss
4.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits
0
none known

Summary

Traefik is an HTTP reverse proxy and load balancer. Prior to version 2.4.13, there exists a potential header vulnerability in Traefik's handling of the Connection header. Active exploitation of this issue is unlikely, as it requires that a removed header would lead to a privilege escalation, however, the Traefik team has addressed this issue to prevent any potential abuse. If one has a chain of Traefik middlewares, and one of them sets a request header, then sending a request with a certain Connection header will cause it to be removed before the request is sent. In this case, the backend does not see the request header. A patch is available in version 2.4.13. There are no known workarounds aside from upgrading.

Patch / fix

  • go github.com/traefik/traefik/v2 2.4.13
  • traefik traefik 2.4.13
  • traefik Arch Linux 2.4.13-1

arch linux advisories AVG-2252

Exploit prediction

1.10% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P
GitHub 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
go github.com/traefik/traefik/v2
<2.4.13
2.4.13
go github.com/traefik/traefik
<=1.7.30
all versions
 no fix listed

Affected products

  • traefik traefik

Classification

Weakness
  • CWE-913 Improper Control of Dynamically-Managed Code Resources

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.