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TI-2026-64880 Aliases CVE-2026-100724GHSA-9hc9-gcfq-xg98

http4k before 6.49.0.0 Host Header Routing Bypass via reverseProxy

Priority LOW 28CWE-444Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
None · None · None
Fix status
Partial Red Hat: 1 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat.

Summary

http4k (Maven package org.http4k:http4k-core) before 6.49.0.0, 5.42.0.0 and 4.51.0.0 uses substring (Contains) matching on the Host header by default in reverseProxy() and reverseProxyRouting() when dispatching to configured virtual hosts. If these functions are deployed as a public-facing inbound HTTP handler with two or more configured virtual hosts, a remote attacker can supply a Host header that merely contains a configured vhost name (for example Host: admin.evil.com for a vhost configured as "admin") and be routed to that vhost, bypassing routing-based authorization. The intended outbound-dispatch and test-time uses, where the Host value is set by the calling application, are not affected.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00344 28th percentileScored 2026-11-07
Fix Partial http4k (http4k): 6.49.0.0, 5.42.0.0, 4.51.0.0Red Hat: 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
http4khttp4k6.0.0.0 to before 6.49.0.06.49.0.0Patch availableCNA
http4khttp4k5.0.0.0 to before 5.42.0.05.42.0.0Patch availableCNA
http4khttp4kbefore 4.51.0.04.51.0.0Patch availableCNA
  • http4k Vendorhttp4k Affected 6.0.0.0 to before 6.49.0.0 Fixed in 6.49.0.0 Patch available CNA
  • http4k Vendorhttp4k Affected 5.0.0.0 to before 5.42.0.0 Fixed in 5.42.0.0 Patch available CNA
  • http4k Vendorhttp4k Affected before 4.51.0.0 Fixed in 4.51.0.0 Patch available CNA

Remediation

  • Fix · CNA http4k (http4k) Fixed in 6.49.0.0
  • Fix · CNA http4k (http4k) Fixed in 5.42.0.0
  • Fix · CNA http4k (http4k) Fixed in 4.51.0.0

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    http4k 4.51.0.0, 5.42.0.0

    3 records Highest priority Priority LOW 3 LOW

    Other records, highest priority first

    • TI-2026-64972 http4k before 6.48.0.0 Digest Authentication Replay Protection BypassPriority LOW 36
    • TI-2026-64881 http4k before 6.48.0.0 Cookie Scoping Bypass via BasicCookieStoragePriority LOW 36
    Show all 3 records →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Fuse 7AffectedNo fix planned: Out of support scope

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-100724
  2. 2026-10-03 Alias added: GHSA-9hc9-gcfq-xg98
  3. 2026-10-29 Affected versions changed · CNA
  4. 2026-11-04 Affected versions changed · Red Hat
  5. 2026-11-04 CVSS score added · Red Hat

References

Patch 2

Advisory 1

  • TI-2024-36944 http4k has a potential XXE (XML External Entity Injection) vulnerability CVSS 3.1CRITICAL 9.8
  • TI-2026-83683 Missing body integrity check in http4k Digest auth-int CVSS 4.0HIGH 8.2
  • TI-2026-38700 http4k: Unbounded gzip decompression in `ServerFilters.GZip` / `RequestFilters.GunZip` allowed memory-exhaustion DoS CVSS 3.1HIGH 7.5
  • TI-2026-39062 http4k: `DigestAuthProvider.verify` did not bind to request URI CVSS 3.1HIGH 8.1
  • TI-2026-64972 http4k before 6.48.0.0 Digest Authentication Replay Protection Bypass CVSS 4.0HIGH 8.2
  • TI-2026-64881 http4k before 6.48.0.0 Cookie Scoping Bypass via BasicCookieStorage CVSS 4.0HIGH 8.3
See all 8 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences