CVE-2021-32813
Drop Headers via Malicious Connection Header
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Drop Headers via Malicious Connection Header
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.
- Record
CVE-2021-32813- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-913
- Updated
- 2026-11-02
EUVDEUVD-2021-1790
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.
- Record
EUVD-2021-1790- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-m697-4v8f-55qg
Header dropping in traefik
Impact
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.
Details
If you have a chain of Traefik middlewares, and one of them sets a request header Important-Security-Header, then sending a request with the following Connection header will cause it to be removed before the request was sent:
curl 'https://example.com' -H "Connection: Important-Security-Header" -0
In this case, the backend does not see the request header Important-Security-Header.
Patches
Traefik v2.4.x: https://github.com/traefik/traefik/releases/tag/v2.4.13
Workarounds
No.
For more information
If you have any questions or comments about this advisory, open an issue.
- Record
GHSA-m697-4v8f-55qg- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-913
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2021-32813- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 6.8 Medium
AV:N/AC:M/Au:N/C:P/I:P/A:P - Weakness
- CWE-913
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-32813- CVSS 3.1
- 8.1 High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-m697-4v8f-55qg
Header dropping in traefik
Impact
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.
Details
If you have a chain of Traefik middlewares, and one of them sets a request header Important-Security-Header, then sending a request with the following Connection header will cause it to be removed before the request was sent:
curl 'https://example.com' -H "Connection: Important-Security-Header" -0
In this case, the backend does not see the request header Important-Security-Header.
Patches
Traefik v2.4.x: https://github.com/traefik/traefik/releases/tag/v2.4.13
Workarounds
No.
For more information
If you have any questions or comments about this advisory, open an issue.
- Record
GHSA-m697-4v8f-55qg- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N - Weakness
- CWE-913
- Updated
- 2026-11-02
OSVGO-2022-0923 No score
Header dropping in traefik in github.com/traefik/traefik
Header dropping in traefik in github.com/traefik/traefik
- Record
GO-2022-0923- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/traefik/traefik/v2Go |
before 2.4.13 | 2.4.13 |
github.com/traefik/traefikGo |
through 1.7.30 | None known |
github.com/traefik/traefikGo |
All versions | None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-32813 is a medium vulnerability (CVSS 4.8) in Traefik, published August 3, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.10%, the 65th percentile. Fixed in github.com/traefik/traefik/v2 2.4.13.