High-severity authentication bypass in widely used Apache Tomcat; can enable unauthorized access across many enterprise deployments.
CVE-2026-86248
Apache Tomcat CLIENT_CERT auth bypass permits unauthorized access.
Is CVE-2026-86248 being exploited?
Not confirmed. CVE-2026-86248 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.
How severe is CVE-2026-86248?
CVE-2026-86248 is rated Critical with a CVSS score of 9.8. 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-2026-86248?
Yes. A fix has been recorded for CVE-2026-86248. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-86248 affect?
CVE-2026-86248 affects Apache Tomcat 11.0.0-M14 through 11.0.25, Apache Tomcat 10.1.22 through 10.1.59, Apache Tomcat 9.0.92 through 9.0.121. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-86248?
Upgrade to Tomcat 11.0.26, 10.1.60, or 9.0.122 immediately.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Bypasses CLIENT_CERT authentication, allowing attackers to access protected resources and impersonate clients remotely.
Immediate action required
- affected>= 11.0.0-M14 and <= 11.0.25
- affected>= 10.1.22 and <= 10.1.59
- affected>= 9.0.92 and <= 9.0.121
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.