Red Hat Security Advisory: multicluster engine for Kubernetes v2.8.9 security update

Critical

A flaw was found in the Konnectivity proxy-server configuration for hosted control planes. The agent-facing listener was started without --cluster-ca-cert (and without token-based agent authentication), so client certificates were not validated. A remote attacker who can reach the Konnectivity cluster endpoint could connect as an unauthenticated agent, join the routing pool, and potentially proxy, inspect, modify, or drop control-plane-to-node traffic.

CWE-306 - Missing Authentication for Critical Function

A flaw was found in the cluster-proxy service-proxy component used in Red Hat Advanced Cluster Management for Kubernetes (RHACM) and multicluster-engine (MCE). The service-proxy appends impersonation group headers to proxied requests without first removing caller-supplied values, and the spoke ServiceAccount holds unrestricted impersonation permissions. An authenticated hub principal can inject an Impersonate-Group header to escalate to cluster-admin on every managed cluster.

CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')

A flaw was found in golang.org/x/net/html. A remote attacker could exploit this vulnerability by providing specially crafted HTML. When this arbitrary HTML is parsed and rendered, it can result in an unexpected HTML tree, bypassing input sanitization. This can be leveraged to execute Cross-Site Scripting (XSS) attacks, potentially leading to arbitrary code execution in applications that use the affected component.

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

A flaw was found in golang.org/x/net/html. When arbitrary HTML is parsed and then rendered, it can result in an unexpected HTML tree. This allows an attacker to bypass HTML sanitization mechanisms, leading to Cross-Site Scripting (XSS) attacks in applications. Such attacks can result in information disclosure or arbitrary code execution.

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

A flaw was found in the `crypto/x509` package of `golang`. This vulnerability allows a remote attacker to cause a Denial of Service (DoS) by presenting a specially crafted X.509 certificate with a large number of DNS Subject Alternative Name (SAN) entries. The certificate verification process, specifically the `VerifyHostname` function, incurs excessive computational overhead due to repeated string operations when processing these entries. This can lead to a significant performance degradation or unresponsiveness of systems validating such certificates.

CWE-606 - Unchecked Input for Loop Condition

A flaw was found in OpenTelemetry-Go, the Go implementation of OpenTelemetry. A remote attacker can exploit this vulnerability by sending multiple 'baggage' header lines. The system's independent parsing and aggregation of each header field-value across multiple values can lead to amplified CPU and memory allocations, resulting in a Denial of Service (DoS).

CWE-770 - Allocation of Resources Without Limits or Throttling

A flaw was found in the `net` package of Go (golang), specifically when using the `LookupCNAME` function with the `cgo` DNS resolver. A remote attacker could exploit this by providing a very long Canonical Name (CNAME) response. This can trigger a double-free of C memory, leading to a crash and a Denial of Service (DoS) for the affected application.

CWE-1341 - Multiple Releases of Same Resource or Handle

A flaw was found in golang.org/x/net/idna. ToASCII and ToUnicode incorrectly accept Punycode-encoded labels that decode to an ASCII-only hostname (for example, xn--example-.com returns example.com instead of an error). Applications that validate the ASCII form then convert to Unicode may grant access to a restricted hostname the ASCII check would have rejected.

CWE-1289 - Improper Validation of Unsafe Equivalence in Input