CVE-2023-41332 in Cilium
Summary
by MITRE • 09/27/2023
Cilium is a networking, observability, and security solution with an eBPF-based dataplane. In Cilium clusters where Cilium's Layer 7 proxy has been disabled, creating workloads with `policy.cilium.io/proxy-visibility` annotations (in Cilium >= v1.13) or `io.cilium.proxy-visibility` annotations (in Cilium <= v1.12) causes the Cilium agent to segfault on the node to which the workload is assigned. Existing traffic on the affected node will continue to flow, but the Cilium agent on the node will not able to process changes to workloads running on the node. This will also prevent workloads from being able to start on the affected node. The denial of service will be limited to the node on which the workload is scheduled, however an attacker may be able to schedule workloads on the node of their choosing, which could lead to targeted attacks. This issue has been resolved in Cilium versions 1.14.2, 1.13.7, and 1.12.14. Users unable to upgrade can avoid this denial of service attack by enabling the Layer 7 proxy.
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Analysis
by VulDB Data Team • 09/27/2023
The vulnerability described in CVE-2023-41332 represents a critical denial of service weakness within the Cilium networking solution that leverages eBPF technology for its data plane operations. This issue specifically targets clusters where the Layer 7 proxy functionality has been disabled, creating a scenario where certain workload annotations can trigger a segmentation fault in the Cilium agent process. The flaw manifests when workloads are deployed with either `policy.cilium.io/proxy-visibility` annotations in Cilium versions 1.13 and later, or `io.cilium.proxy-visibility` annotations in earlier versions. The technical implementation of this vulnerability stems from improper handling of these annotations within the agent's processing pipeline, leading to memory access violations that cause the process to terminate abruptly.
The operational impact of this vulnerability extends beyond simple service disruption to encompass complete agent malfunction on affected nodes. When the segmentation fault occurs, the Cilium agent becomes unable to process any further workload changes or updates on that specific node, effectively rendering the node's networking and security policies static and unresponsive. This creates a cascading effect where new workloads cannot be scheduled onto the affected node, while existing network traffic continues to flow through the system but without the ability to process new policy updates or modifications. The vulnerability's targeted nature means that an attacker could potentially schedule malicious workloads onto specific nodes of their choosing, creating localized denial of service conditions that could be used to disrupt services or isolate particular portions of the cluster infrastructure.
From a cybersecurity perspective, this vulnerability aligns with CWE-119 which addresses "Improper Access to Memory" and represents a classic buffer overflow or memory corruption issue that leads to process termination. The attack surface is particularly concerning as it can be exploited through legitimate cluster scheduling mechanisms, making it difficult to distinguish from normal operational behavior. The ATT&CK framework categorizes this as a denial of service attack using process injection techniques, where the vulnerability enables an attacker to cause system instability through carefully crafted workload annotations. The remediation path involves upgrading to patched versions of Cilium, with releases 1.14.2, 1.13.7, and 1.12.14 providing the necessary fixes. Alternative mitigation strategies include enabling the Layer 7 proxy functionality, which bypasses the problematic code path entirely. Organizations should also implement monitoring for unusual workload scheduling patterns and consider network segmentation to limit the potential impact of such attacks. The vulnerability demonstrates the critical importance of proper input validation in security-critical components and highlights the need for comprehensive testing of annotation-based configuration mechanisms in container orchestration platforms.