Widely used Undertow in enterprise Java stacks; enables request smuggling, risking data exposure and cache manipulation.
CVE-2026-28369
HTTP header leading spaces enable Undertow request smuggling.
Is CVE-2026-28369 being exploited?
Not confirmed. CVE-2026-28369 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.68% probability of exploitation in the next 30 days.
How severe is CVE-2026-28369?
CVE-2026-28369 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-28369?
Yes. A fix has been recorded for CVE-2026-28369. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-28369 affect?
CVE-2026-28369 affects Undertow (Java web server), JBoss/WildFly deployments, Java EE stacks. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-28369?
Patch Undertow to fixed version
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attacker can bypass controls, access restricted data, or manipulate web caches via request smuggling.
Patch when possible