A denial-of-service vulnerability was identified in multiple TLS listeners in Rancher. Both the cattle-cluster-agent component running in downstream clusters and the Rancher server itself use the dynamiclistener library to serve TLS traffic. Without an effective CN filter configured, dynamiclistener automatically appended to each serving certificate any hostname presented via Server Name Indication (SNI) in incoming TLS requests.
An unauthenticated attacker with network access within the affected cluster could send a large number of TLS requests with distinct hostnames, causing the serving certificate to accumulate an unbounded number of Subject Alternative Names (SANs). Eventually, the certificate grows large enough that TLS handshakes fail with an excessive message size error, causing a denial of service on the affected listeners.
Metrics
Affected Vendors & Products
References
History
Wed, 05 Aug 2026 14:30:00 +0000
| Type | Values Removed | Values Added |
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| Metrics |
ssvc
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Wed, 05 Aug 2026 10:15:00 +0000
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| First Time appeared |
Suse
Suse rancher |
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| Vendors & Products |
Suse
Suse rancher |
Wed, 05 Aug 2026 09:45:00 +0000
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| Weaknesses | CWE-770 |
Wed, 05 Aug 2026 08:15:00 +0000
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| Description | A denial-of-service vulnerability was identified in multiple TLS listeners in Rancher. Both the cattle-cluster-agent component running in downstream clusters and the Rancher server itself use the dynamiclistener library to serve TLS traffic. Without an effective CN filter configured, dynamiclistener automatically appended to each serving certificate any hostname presented via Server Name Indication (SNI) in incoming TLS requests. An unauthenticated attacker with network access within the affected cluster could send a large number of TLS requests with distinct hostnames, causing the serving certificate to accumulate an unbounded number of Subject Alternative Names (SANs). Eventually, the certificate grows large enough that TLS handshakes fail with an excessive message size error, causing a denial of service on the affected listeners. | |
| Title | Unauthenticated Denial-of-Service via TLS SAN Stuffing in Rancher and cattle-cluster-agent | |
| References |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: suse
Published:
Updated: 2026-08-05T19:05:26.627Z
Reserved: 2026-06-18T09:26:55.987Z
Link: CVE-2026-55996
Updated: 2026-08-05T13:40:27.785Z
No data.
No data.
OpenCVE Enrichment
Updated: 2026-08-05T10:00:03Z