CVE-2026-42273: Heimdall: Case-sensitive host matching may lead to policy bypass

Severity: high (CVSS 7.8 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-08 · updated 2026-10-26
Weakness: CWE-178

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.

Affected products

dadrus heimdall: before 0.17.14

References

https://github.com/dadrus/heimdall/commit/3d05e56a9e7ef0355f17482b4322054af4e85943
https://github.com/dadrus/heimdall/pull/3208
https://github.com/dadrus/heimdall/releases/tag/v0.17.14
https://github.com/dadrus/heimdall/security/advisories/GHSA-72h4-mxfc-jx37

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