Affects widely used Apache Tomcat versions; allows security-constraint bypass exposing protected web resources across many deployments; high CVSS (9.1).
CVE-2026-59083
Tomcat URL hex-decoding flaw permits security-constraint bypass in multiple versions.
Is CVE-2026-59083 being exploited?
Not confirmed. CVE-2026-59083 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 0.37% probability of exploitation in the next 30 days.
How severe is CVE-2026-59083?
CVE-2026-59083 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-2026-59083?
Yes. A fix has been recorded for CVE-2026-59083. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-59083 affect?
CVE-2026-59083 affects Apache Tomcat 11.0.0-M1 through 11.0.23, Apache Tomcat 10.1.0-M1 through 10.1.56, Apache Tomcat 9.0.0.M1 through 9.0.119, Apache Tomcat 8.5.0 through 8.5.100. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-59083?
Upgrade to 11.0.24, 10.1.57 or 9.0.120 immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Crafted percent-encoded URLs can bypass Tomcat rewrite security constraints, allowing unauthorized access to protected web resources.
Immediate action required
- affected>= 11.0.0-M1 and <= 11.0.23
- affected>= 10.1.0-M1 and <= 10.1.56
- affected>= 9.0.0.M1 and <= 9.0.119
- 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.