Red Hat Security Advisory: multicluster engine for Kubernetes v2.10.4 security update

Critical

A flaw was found in the archive/tar package in the Go standard library. tar.Reader does not set a maximum size on the number of sparse region data blocks in GNU tar pax 1.0 sparse files. A specially crafted tar archive with a pax header indicating a big number of sparse regions can cause a Go program to try to allocate a large amount of memory, causing an out-of-memory condition and resulting in a denial of service.

CWE-770 - Allocation of Resources Without Limits or Throttling

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 BuildKit, a toolkit for converting source code to build artifacts. An untrusted BuildKit frontend can be leveraged to craft a malicious API message, allowing files to be written outside of the designated BuildKit state directory. This vulnerability, which is a form of arbitrary file write, could enable an attacker to execute unauthorized code or escalate their privileges on the system. This issue arises when custom BuildKit frontends are used with specific configuration options.

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

A flaw was found in BuildKit. Insufficient validation of Git URL fragment subdirectory components may allow a remote attacker to access files outside the checked-out Git repository root. This access is limited to files on the same mounted filesystem. This vulnerability could lead to unauthorized information disclosure.

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

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 Go JOSE, a library for handling JSON Web Encryption (JWE) objects. A remote attacker could exploit this vulnerability by providing a specially crafted JWE object. When decrypting such an object, if a key wrapping algorithm is specified but the encrypted key field is empty, the application can crash. This leads to a denial of service (DoS), making the affected service unavailable to legitimate users.

CWE-131 - Incorrect Calculation of Buffer Size