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CVE-2026-39858

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a high severity authentication bypass vulnerability in Traefik's ForwardAuth and snippet-based authentication middleware. Traefik's forwarded-header sanitization logic targets only canonical header names (e.g., X-Forwarded-Proto) and does not strip or normalize alias variants that use underscores instead of dashes (e.g., X_Forwarded_Proto). These unsanitized alias headers are forwarded
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:e6fa19b57541a6b55de4f1e6b9b72a275a7877c3ce63180092fc169db2cb726c
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
3

Preserved source conflicts

No provider value was silently selected as the winner.

affected · 2 assertions

{"collectionURL":"https://catalog.redhat.com/software/containers/","cpes":["cpe:/a:redhat:openshift_devspaces:3.28::el9"],"defaultStatus":"affected","packageName":"devspaces/traefik-rhel9","product":"Red Hat OpenShift Dev Spaces 3.28","vendor":"Red Hat","versions":[{"lessThan":"*","status":"unaffected","version":"1779786779","versionType":"rpm"}]}

  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/affected/0

{"product":"traefik","vendor":"traefik","versions":[{"status":"affected","version":"< 2.11.43"},{"status":"affected","version":">= 3.0.0-beta1, < 3.6.14"},{"status":"affected","version":">= 3.7.0-ea.1, < 3.7.0-rc.2"}]}

  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/affected/0
cvss · 2 assertions

{"metric":{"attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":7.8,"baseSeverity":"HIGH","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"HIGH","subIntegrityImpact":"HIGH","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE"},"metric_type":"cvssV4_0"}

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/metrics/0/cvssV4_0

{"metric":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":8.2,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}

  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/metrics/1/cvssV3_1
cwe · 3 assertions

{"cweId":"CWE-306","description":"CWE-306: Missing Authentication for Critical Function","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/problemTypes/1/descriptions/0

{"cweId":"CWE-290","description":"CWE-290: Authentication Bypass by Spoofing","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/problemTypes/0/descriptions/0

{"cweId":"CWE-289","description":"Authentication Bypass by Alternate Name","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/problemTypes/0/descriptions/0

Affected products and versions

2 source assertions
{"collectionURL":"https://catalog.redhat.com/software/containers/","cpes":["cpe:/a:redhat:openshift_devspaces:3.28::el9"],"defaultStatus":"affected","packageName":"devspaces/traefik-rhel9","product":"Red Hat OpenShift Dev Spaces 3.28","vendor":"Red Hat","versions":[{"lessThan":"*","status":"unaffected","version":"1779786779","versionType":"rpm"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/affected/0
{"product":"traefik","vendor":"traefik","versions":[{"status":"affected","version":"< 2.11.43"},{"status":"affected","version":">= 3.0.0-beta1, < 3.6.14"},{"status":"affected","version":">= 3.7.0-ea.1, < 3.7.0-rc.2"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/affected/0

Provider-owned CVSS observations

2 source assertions
{"metric":{"attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":7.8,"baseSeverity":"HIGH","privilegesRequired":"NONE","subAvailabilityImpact":"NONE","subConfidentialityImpact":"HIGH","subIntegrityImpact":"HIGH","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE"},"metric_type":"cvssV4_0"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/metrics/0/cvssV4_0
{"metric":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":8.2,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N","version":"3.1"},"metric_type":"cvssV3_1"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/metrics/1/cvssV3_1

CWE assertions

3 source assertions
{"cweId":"CWE-306","description":"CWE-306: Missing Authentication for Critical Function","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/problemTypes/1/descriptions/0
{"cweId":"CWE-290","description":"CWE-290: Authentication Bypass by Spoofing","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/problemTypes/0/descriptions/0
{"cweId":"CWE-289","description":"Authentication Bypass by Alternate Name","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/problemTypes/0/descriptions/0

Source references

8 source assertions
{"tags":["vendor-advisory","x_refsource_REDHAT"],"url":"https://access.redhat.com/errata/RHSA-2026:21772"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/references/3
{"tags":["vdb-entry","x_refsource_REDHAT"],"url":"https://access.redhat.com/security/cve/CVE-2026-39858"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/references/0
{"name":"RHBZ#2464234","tags":["issue-tracking","x_refsource_REDHAT"],"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2464234"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/references/1
{"name":"https://github.com/traefik/traefik/releases/tag/v2.11.43","tags":["x_refsource_MISC"],"url":"https://github.com/traefik/traefik/releases/tag/v2.11.43"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/references/1
{"name":"https://github.com/traefik/traefik/releases/tag/v3.6.14","tags":["x_refsource_MISC"],"url":"https://github.com/traefik/traefik/releases/tag/v3.6.14"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/references/2
{"name":"https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2","tags":["x_refsource_MISC"],"url":"https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/references/3
{"name":"https://github.com/traefik/traefik/security/advisories/GHSA-5m6w-wvh7-57vm","tags":["x_refsource_CONFIRM"],"url":"https://github.com/traefik/traefik/security/advisories/GHSA-5m6w-wvh7-57vm"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/cna/references/0
{"tags":["x_sadp-csaf-vex"],"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39858.json"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:3536b89498c08beb575bfb51d334f6239a1ef99a886e6b1642e0dfee7fec70ff · sha256:2f9626c707bc3a88… · /containers/adp/1/references/2

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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