How severe is CVE-2026-42273?

CVE-2026-42273 has a CVSS 4.0 base score of 7.8, rated high severity.

Is CVE-2026-42273 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-42273?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-42273 have an EU (EUVD) identifier?

Yes. CVE-2026-42273 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28509.

When was CVE-2026-42273 published?

CVE-2026-42273 was published on 2026-05-08 and last updated on 2026-06-17.

CVE-2026-42273

CVE-2026-42273 is a high-severity vulnerability with a CVSS 4.0 base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-178.

Key facts

Severity: High (CVSS 4.0 base score 7.8)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-28509
Weakness: CWE-178
Published: 2026-05-08
Last modified: 2026-06-17

Description

Heimdall is a cloud native Identity Aware Proxy and Access Control Decision service. Prior to version 0.17.14, Heimdall performs host matching in a case-sensitive manner, while HTTP hostnames are case-insensitive. This discrepancy can result in heimdall failing to match a rule for a request host that differs only in letter casing, potentially causing the request to be classified differently than intended. This issue has been patched in version 0.17.14.

Frequently asked questions

What is CVE-2026-42273?: Heimdall is a cloud native Identity Aware Proxy and Access Control Decision service. Prior to version 0.17.14, Heimdall performs host matching in a case-sensitive manner, while HTTP hostnames are case-insensitive. This discrepancy can result in heimdall failing to match a rule for a request host that differs only in letter casing, potentially causing the request to be classified differently than intended. This issue has been patched in version 0.17.14.
How severe is CVE-2026-42273?: CVE-2026-42273 has a CVSS 4.0 base score of 7.8, rated high severity.
Is CVE-2026-42273 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-42273?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42273 have an EU (EUVD) identifier?: Yes. CVE-2026-42273 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28509.
When was CVE-2026-42273 published?: CVE-2026-42273 was published on 2026-05-08 and last updated on 2026-06-17.

References

Other CWE-178 vulnerabilities

CVE-2026-54763 — Critical (CVSS 10.0): Traefik is an HTTP reverse proxy and load balancer. Prior to v2.11.51, v3.6.22, and v3.7.6, Traefik's BasicAuth,…
CVE-2026-40453 — Critical (CVSS 9.9): The fix for CVE-2025-27636 added setLowerCase(true) to HttpHeaderFilterStrategy so that case-variant header names such…
CVE-2026-47323 — Critical (CVSS 9.8): Camel-CXF and Camel-Knative Message Header Injection via Missing Inbound Filtering The CXF and Knative…
CVE-2024-5699 — Critical (CVSS 9.8): In violation of spec, cookie prefixes such as `__Secure` were being ignored if they were not correctly capitalized - by…
CVE-2023-3545 — Critical (CVSS 9.8): Improper sanitisation in `main/inc/lib/fileUpload.lib.php` in Chamilo LMS <= v1.11.20 on Windows and Apache…
CVE-2022-29604 — Critical (CVSS 9.8): An issue was discovered in ONOS 2.5.1. An intent with an uppercase letter in a device ID shows the CORRUPT state, which…

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