CVE-2022-49809 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
net/x25: Fix skb leak in x25_lapb_receive_frame()
x25_lapb_receive_frame() using skb_copy() to get a private copy of skb, the new skb should be freed in the undersized/fragmented skb error handling path. Otherwise there is a memory leak.
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Analysis
by VulDB Data Team • 11/07/2025
The vulnerability identified as CVE-2022-49809 represents a memory leak issue within the Linux kernel's network subsystem, specifically affecting the x25 protocol implementation. This flaw exists in the net/x25 subsystem where the x25_lapb_receive_frame() function handles incoming network frames. The issue stems from improper memory management practices during error handling scenarios, creating a persistent memory leak that can accumulate over time and potentially lead to system instability or resource exhaustion.
The technical root cause of this vulnerability lies in the function's use of skb_copy() to create a private copy of network packets for processing. While the kernel correctly allocates new sk_buff structures for these copies, the error handling path fails to properly free the duplicated sk_buff when encountering undersized or fragmented packet conditions. This violates fundamental memory management principles and creates a classic resource leak pattern. The flaw is categorized under CWE-401 as a failure to release memory after it has been allocated, specifically manifesting as an improper cleanup in error handling code paths.
The operational impact of this vulnerability extends beyond simple memory consumption issues. When the x25_lapb_receive_frame() function processes malformed or incorrectly sized network frames, the system experiences gradual memory depletion as each failed packet processing leaves behind unreclaimed sk_buff structures. This memory leak can accumulate particularly in environments with high network traffic or repeated malformed packet processing, potentially leading to system performance degradation, increased swap usage, or in severe cases, system crashes or denial of service conditions. The vulnerability affects systems running Linux kernel versions where the x25 protocol stack is active, particularly those implementing X.25 network services or supporting legacy telecommunications protocols.
Mitigation strategies for CVE-2022-49809 focus on applying the official kernel patch that corrects the memory leak by ensuring proper cleanup of sk_buff structures in all error handling paths. System administrators should prioritize updating their Linux kernel installations to versions containing the fix, typically kernel version 5.19 or later where this vulnerability was resolved. Additionally, monitoring network traffic for malformed x25 frames can help identify systems where this vulnerability might be exploited, though the leak is more likely to occur through normal network processing rather than active attack vectors. Network administrators should also implement proper memory monitoring tools to detect gradual memory consumption patterns that might indicate this vulnerability's presence in unpatched systems, aligning with ATT&CK technique T1490 for resource exhaustion attacks. The fix demonstrates proper defensive programming practices by ensuring that all allocated resources are properly released regardless of execution path taken during error conditions, following established kernel development best practices for memory management and robust error handling.