What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-12-04 · updated 2026-06-17
• Weakness: CWE-772

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`.

Affected products

• Traefik: through 2.10.5; 3.0.0-beta1, 3.0.0-beta2, 3.0.0-beta3, 3.0.0-beta4

References

• 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://github.com/traefik/traefik/security/advisories/GHSA-8g85-whqh-cr2f
• https://www.cloudflare.com/learning/ddos/ddos-attack-tools/slowloris
• 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

Get alerted when CVE-2023-47124 or the next vulnerability affects your stack