CVE-2023-32187Network attack vector

Denial of service via TLS SAN stuffing

Published Sep 18, 2023 · Updated Sep 25, 2024

Resource exhaustion in Rancher K3s allows remote attackers to block new client connections via TLS handshakes on TCP port 6443. The apiserver's dynamiclistener accepts unfiltered client-requested hostnames and IP addresses as certificate SAN entries until the certificate exceeds TLS client size limits. Network access to port 6443 is sufficient without authentication; running servers remain up, but kubectl, server, and agent clients cannot establish new connections.

CVSS severity7.5
High
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Rancher K3s allows remote attackers to block new client connections via TLS handshakes on TCP port 6443. The apiserver's dynamiclistener accepts unfiltered client-requested hostnames and IP addresses as certificate SAN entries until the certificate exceeds TLS client size limits. Network access to port 6443 is sufficient without authentication; running servers remain up, but kubectl, server, and agent clients cannot establish new connections.

The record

CVE
CVE-2023-32187
Published
Sep 18, 2023
Updated
Sep 25, 2024
Vendor
Rancher
Product
K3s
Classifications
CWE-770, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 18, 2023CVE publishedPublication date reported by the CVE source.
  2. Sep 25, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.24.0 <1.24.17+k3s1
  2. Affected versionversion=1.25.0 <1.25.13+k3s1
  3. Affected versionversion=1.26.0 <1.26.8+k3s1
  4. Affected versionversion=1.27.0 <1.27.5+k3s1
  5. Affected versionversion=1.28.0 <1.28.1+k3s1
  6. Affected versionversion=sev1.27.0 <v1.27.5+k3s1
  7. Affected versionversion=v1.24.0 <v1.24.17+k3s1
  8. Affected versionversion=v1.25.0 <v1.25.13+k3s1
  9. Affected versionversion=v1.26.0 <v1.26.8+k3s1
  10. Affected versionversion=v1.28.0 <v1.28.1+k3s1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rancher · K3sversion=1.24.0 <1.24.17+k3s1; version=1.25.0 <1.25.13+k3s1; version=1.26.0 <1.26.8+k3s1; version=1.27.0 <1.27.5+k3s1; version=1.28.0 <1.28.1+k3s1; version=sev1.27.0 <v1.27.5+k3s1; version=v1.24.0 <v1.24.17+k3s1; version=v1.25.0 <v1.25.13+k3s1; version=v1.26.0 <v1.26.8+k3s1; version=v1.28.0 <v1.28.1+k3s1

Published CVSS scores

7.5GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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