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VulnerabilityPublished Updated

CVE-2026-88879: Traefik is an HTTP reverse proxy and load balancer

Affects traefikSource GCVE Database

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Not known to be exploited · CVSS 8.2 High : upgrade to 3.7.12 or 2.11.56 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score
8.2High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 22% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.7.12, 2.11.56
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 10 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade traefik/traefik to 3.7.12 or 2.11.56.

Affected software

ProductAffectedFixed in
GitHubtraefik/traefikpkg:github/traefik/traefikOther threatsAffected
  • <2.11.56
  • <3.7.12
Fixed in
  • 2.11.56
  • 3.7.12

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in Traefik versions v2.11.56 and v3.7.12. To fully mitigate the vulnerability, administrators must explicitly configure the aliasHeadersStrategy entry-point option to 'delete' or 'reject' to prevent dot-form header aliases from bypassing middleware protections. Unmaintained versions will not receive patches, so upgrading to a maintained version and applying the configuration change is recommended.

Description

Traefik versions v1.x, v2.x through v2.11.55, and v3.0.0 through v3.7.11 have a header canonicalization issue where headers with dots, underscores, and dashes are treated as distinct. This allows an attacker to smuggle alternate forms of headers past Traefik's middleware, potentially causing backend services to use attacker-supplied header values instead of those asserted by Traefik. This can lead to privilege escalation or identity spoofing. The issue is fixed in v2.11.56 and v3.7.12 with a new configuration option that must be explicitly enabled to take effect. Unmaintained versions will not receive patches.

References

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