Undertow is Vulnerable to HTTP Request/Response Smuggling
A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain proxy servers, such as older versions of Apache Traffic Server and Google Cloud Classic Application Load Balancer, potentially leading to unauthorized access or manipulation of web requests.
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describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-28367US | critical9.1 | — | ||
A flaw was found in Undertow. A remote attacker can exploit this vulnerability by sending `\r\r\r` as a header block terminator. This can be used for request smuggling with certain… | ||||
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references
External citations — patches, advisories, analysis.
- https://access.redhat.com/errata/RHSA-2026:25125WEB
- https://access.redhat.com/errata/RHSA-2026:25126WEB
- https://access.redhat.com/security/cve/CVE-2026-28367WEB
- https://bugzilla.redhat.com/show_bug.cgi?id=2443260WEB
- https://github.com/undertow-io/undertowPACKAGE
- https://nvd.nist.gov/vuln/detail/CVE-2026-28367ADVISORY
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