CVE-2026-77791

Apache Tomcat: DoS via busy wait during WebSocket close

HIGH
7.5
CVSS Score
Published: September 23, 2026 at 11:20 AM UTC
Updated: September 23, 2026 at 07:30 PM UTC
1 product affected across 1 vendorTomcat

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Severity
HIGH7.5
Exploit prediction
EPSS 0.7%
SSVC
No known exploit

Description

Uncontrolled Resource Consumption vulnerability in Apache Tomcat during sending of WebSocket close message enabled a DoS attack. This issue affects Apache Tomcat: from 11.0.0-M5 through 11.0.25, from 10.1.8 through 10.1.59, from 9.0.74 through 9.0.121. The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.88 through 8.5.100. Other unsupported versions may also be affected. Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

10.1.8 ≤ v ≤ 10.1.5911.0.0-M5 ≤ v ≤ 11.0.258.5.88 ≤ v ≤ 8.5.1009.0.74 ≤ v ≤ 9.0.12110.1.811.0.0-M58.5.889.0.74
Vendor states this is fixed in 7.0.109 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-400

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