CVE-2017-17432 in OpenAFS
Summary
by MITRE
OpenAFS 1.x before 1.6.22 does not properly validate Rx ack packets, which allows remote attackers to cause a denial of service (system crash or application crash) via crafted fields, as demonstrated by an integer underflow and assertion failure for a small MTU value.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 01/17/2023
OpenAFS version 1.x prior to 1.6.22 contains a critical vulnerability in its Rx protocol implementation that fails to properly validate acknowledgment packets. This vulnerability manifests as a lack of proper input validation for Rx ack packet fields, creating a pathway for remote attackers to exploit the system through carefully crafted packet structures. The flaw specifically impacts the handling of network acknowledgment messages within the OpenAFS distributed file system architecture, which is widely deployed in enterprise environments for secure file sharing and authentication services.
The technical exploitation of this vulnerability occurs through integer underflow conditions that arise when processing crafted Rx ack packets with small MTU values. When the system receives malformed acknowledgment packets containing invalid or manipulated field values, the Rx protocol implementation fails to properly validate these inputs before processing them. This validation failure results in an integer underflow condition that ultimately triggers an assertion failure within the OpenAFS kernel modules. The assertion failure causes the system to terminate unexpectedly, leading to either a complete system crash or application-level crash that disrupts normal file service operations.
From an operational impact perspective, this vulnerability presents a significant denial of service threat to OpenAFS deployments that have not yet been patched. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter without requiring authentication or local access to the target system. The consequences extend beyond simple service disruption to potentially compromise the availability of critical file services that many organizations depend upon for business operations. This vulnerability affects the core functionality of OpenAFS, which is used for secure file sharing, authentication, and distributed computing environments where system stability is paramount.
The vulnerability aligns with CWE-191, which addresses integer underflow conditions, and demonstrates characteristics consistent with the ATT&CK technique T1499.004 for network denial of service attacks. Organizations utilizing OpenAFS should prioritize immediate patching to version 1.6.22 or later, which includes proper input validation for Rx ack packet fields and addresses the integer underflow conditions that trigger system crashes. Network segmentation and monitoring of Rx protocol traffic can provide additional defensive measures while awaiting patch deployment, though these approaches do not fully mitigate the risk. The vulnerability underscores the importance of proper input validation in network protocol implementations and highlights the critical need for maintaining up-to-date security patches in distributed systems.