Resource exhaustion in SUSE Rancher
CVE-2026-55996
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.002 (15.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 15.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000
Affected products
- SUSE Rancher — versions 2.11.0, 2.12.0, 2.13.0
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-55996?
- CVE-2026-55996 is a medium-severity vulnerability in SUSE Rancher, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 4.3/10. Published 2026-08-05.
- How severe is CVE-2026-55996?
- Medium severity. CVSS v3 base score is 4.3 out of 10.