CVE-2026-55996: Unauthenticated Denial-of-Service via TLS SAN Stuffing in Rancher and cattle-cluster-agent
SUSE · Rancher
Vendor fix available · Affected: SUSE Rancher · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 15% of scored CVEs
DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- SUSE · Rancherfrom 2.11.0 before 2.11.16; from 2.12.0 before 2.12.12; from 2.13.0 before 2.13.8; from 2.14.0 before 2.14.4
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- SUSE
- Published
- August 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-55996 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.