Threat Intelligence / CVE / CVE-2026-65637

CVE-2026-65637 — Apache Tomcat

CVSS v3.1 9.8 (CRITICAL) · EPSS 0.5% (higher than 42.7% of all scored CVEs) · Priority 6.6/10 · Published 2026-08-25

As of 2026-08-26, CVE-2026-65637 is a CRITICAL-severity vulnerability in Apache Tomcat, CVSS v3.1 9.8, EPSS 0.5% (42.7th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-65637, most recently “Apache Tomcat 11.0.25 Fixes 11 Vulnerabilities Including HTTP/2 DoS, Authorization Bypass, and Auth Fail-Open Flaws — NVD Scores 5 of 11 CRITICAL/HIGH Despite Apache's Low/Moderate Ratings”.

Last updated: 2026-08-26

What is CVE-2026-65637?

Improper Input Validation vulnerability in Apache Tomcat due to incomplete fix for CVE-2026-32990. This issue affects Apache Tomcat: from 11.0.20 through 11.0.24, from 10.1.53 through 10.1.57, from 9.0.115 through 9.0.120. Users are recommended to upgrade to version 11.0.25, 10.1.58 or 9.0.121, which fix the issue.

The record classifies CVE-2026-65637 under weakness class CWE-20. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 19 days ago.

Severity and exploitation probability

CVSS v3.1 base score: 9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST): 0.5% probability of exploitation in the next 30 days, higher than 42.7% of all scored CVEs
CISA KEV: Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority: 6.6/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published: 2026-08-25, last modified 2026-08-26

Is CVE-2026-65637 being exploited?

No public exploitation evidence for CVE-2026-65637 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-08-26. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.

Affected products and versions

Apache Software Foundation: Apache Tomcat

How to fix CVE-2026-65637

Vendor advisory: https://lists.apache.org/thread/djog953z1ohsyt25bdvhfzbmsy22vgcj. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2026-65637

1 tracked threat in the Threadlinqs corpus references CVE-2026-65637, either in the campaign’s CVE list or as an indicator on the campaign record.

Apache Tomcat 11.0.25 Fixes 11 Vulnerabilities Including HTTP/2 DoS, Authorization Bypass, and Auth Fail-Open Flaws — NVD Scores 5 of 11 CRITICAL/HIGH Despite Apache's Low/Moderate Ratings — CRITICAL · 2026-08-26

Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on 2026-08-27. This product uses the NVD API but is not endorsed or certified by the NVD.

Vendor advisory and patch

lists.apache.org — vendor advisory

Full detection coverage & IOCs for threats exploiting CVE-2026-65637 are available via the Threadlinqs MCP server (Purple tier). View plans →

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