Affects widely used Apache Tomcat across multiple versions; critical auth bypass risk.
CVE-2026-55276
Tomcat auth control flow flaw may bypass authorization via logged web.xml.
Is CVE-2026-55276 being exploited?
Not confirmed. CVE-2026-55276 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 0.56% probability of exploitation in the next 30 days.
How severe is CVE-2026-55276?
CVE-2026-55276 is rated Critical with a CVSS score of 9.1. 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-2026-55276?
Yes. A fix has been recorded for CVE-2026-55276. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55276 affect?
CVE-2026-55276 affects Apache Tomcat 8.5.x, 9.x, 10.x, 11.x (M1 to GA). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55276?
Upgrade to fixed versions (11.0.23/10.1.56/9.0.119) immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypass authorization controls in Tomcat due to incorrect control flow when logging effective web.xml; may enable access to restricted resources.
Immediate action required
- affected>= 11.0.0-M1 and <= 11.0.22
- affected>= 10.1.0-M1 and <= 10.1.55
- affected>= 9.0.0.M1 and <= 9.0.118
- affected>= 8.5.0 and <= 8.5.100
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.