Traefik 3.2.0 before 3.7.15 FastProxy Data Race Denial of Service
Only affects Traefik 3.2.0 before 3.7.15 with the experimental FastProxy feature enabled. Fixed in 3.7.15.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Fix
- Fixed in 3.7.15
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
Traefik, a widely used cloud-native reverse proxy and load balancer, is affected when its experimental FastProxy feature is enabled. An unauthenticated attacker can send repeated HTTP/1 protocol upgrade requests, such as WebSocket connections that are opened and aborted, to crash the Traefik process and cause a denial of service.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
Traefik from 3.2.0 before 3.7.15 contains a data race in the experimental FastProxy that allows unauthenticated attackers to crash the process by abusing HTTP/1 protocol upgrades. Attackers can repeatedly open and abort upgraded connections such as WebSocket, corrupting the unsynchronized shared bufio.Reader and triggering an unrecovered panic that terminates Traefik.
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- traefik traefik
From 3.2.0 · fixed in 3.7.15
References 2
GitHub · traefik/traefik
Questions about CVE-2026-119574
What does this mean?
A data race in Traefik's FastProxy feature can trigger an unrecovered panic when a backend answers an HTTP/1 protocol upgrade such as WebSocket. Repeatedly opening and aborting such upgraded connections can crash the whole Traefik process, causing a denial of service.Source: vulncheck.com, github.com
Am I affected, and how do I check?
The affected range is Traefik 3.2.0 up to but not including 3.7.15. Only deployments that enable the experimental FastProxy feature (experimental.fastProxy) are affected. To check, look at the Traefik version and whether experimental.fastProxy is enabled in the configuration.Source: vulncheck.com, github.com
What should I do about it?
Upgrade Traefik to 3.7.15 or later, which contains the fix.Source: vulncheck.com, github.com
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data