CVE-2026-100724

MEDIUMPre-NVD 5.45.4—
EchelonGraph scoreHIGH confidence

Score 5.4 from GitHub Security Advisory published 2026-09-27. A secondary CVSS source baseline 5.4; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 5.4Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
5.4
EG Score
5.4MEDIUMhigh confidence
EG Risk
24
EG Risk 24/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity54% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
25th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 27, 2026

Last Modified

September 30, 2026

Advisory Details (4)

Auto-updated Sep 27, 2026
Patch available. Sources: github, github_commit.
generic

http4k before 6.49.0.0 Host Header Routing Bypass via reverseProxy | Advisories | VulnCheck

https://www.vulncheck.com/advisories/http4k-before-6.49.0.0-host-header-routing-bypass-via-reverseproxy
github_commit Patch Available

commit 54c6385615 (http4k/http4k)

Patch available: http4k/http4k 6.49.0.0 (contains commit 54c6385615)

https://github.com/http4k/http4k/commit/54c6385615
github_commit Patch Available

commit 0121b05537 (http4k/http4k)

Patch available: http4k/http4k 6.39.0.0 (contains commit 0121b05537)

https://github.com/http4k/http4k/commit/0121b05537
github Patch Available

`reverseProxy()` defaulted to substring (`Contains`) matching on `Host`; tightened to `Exact` in v6.49.0.0 · Advisory · http4k/http4k · GitHub

https://github.com/http4k/http4k/security/advisories/GHSA-jrpc-7vxp-69p6

Vendor Advisories for CVE-2026-100724(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.http4k:http4k-core6.0.0.0 ... 6.9.2.0 (90 versions)6.49.0.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 21× in last 7d / 24× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-03 15:07 UTCEG score recompute
  2. 2026-10-03 15:07 UTCGHSA enrichment
  3. 2026-10-03 14:25 UTCEPSS rescore
  4. 2026-10-02 16:02 UTCEG score recompute
  5. 2026-10-02 16:02 UTCGHSA enrichment
  6. 2026-10-01 19:49 UTCEPSS rescore
  7. 2026-10-01 17:00 UTCGHSA enrichment
  8. 2026-09-30 17:47 UTCGHSA enrichment
  9. 2026-09-30 16:27 UTCEG score recompute
  10. 2026-09-30 16:27 UTCGHSA enrichment
  11. 2026-09-30 15:31 UTCEG score recompute
  12. 2026-09-30 15:31 UTCGHSA enrichment
  13. 2026-09-30 15:02 UTCEPSS rescore
  14. 2026-09-29 23:49 UTCEG score recompute
  15. 2026-09-29 23:48 UTCGHSA enrichment
  16. 2026-09-29 15:20 UTCEPSS rescore
  17. 2026-09-29 00:47 UTCEG score recompute
  18. 2026-09-29 00:46 UTCGHSA enrichment
  19. 2026-09-28 13:50 UTCEPSS rescore
  20. 2026-09-28 01:42 UTCEG score recompute
  21. 2026-09-28 01:42 UTCGHSA enrichment
  22. 2026-09-27 02:37 UTCEG score recompute
  23. 2026-09-27 01:53 UTCEG score recompute
  24. 2026-09-27 01:49 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Same product

2 shown

Maven:org.http4k:http4k-core

Frequently asked(5)

What is CVE-2026-100724?
CVE-2026-100724 is a medium vulnerability published on September 27, 2026. 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…
When was CVE-2026-100724 disclosed?
CVE-2026-100724 was first published on September 27, 2026, with the most recent update on September 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100724 actively exploited?
CVE-2026-100724 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (25th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100724?
CVE-2026-100724 has a CVSS base score of 5.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-100724?
A fix for CVE-2026-100724 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-100724 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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