CVE-2022-49587 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
tcp: Fix a data-race around sysctl_tcp_notsent_lowat.
While reading sysctl_tcp_notsent_lowat, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader.
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Analysis
by VulDB Data Team • 07/11/2025
The vulnerability CVE-2022-49587 represents a critical data-race condition within the Linux kernel's TCP implementation that affects the sysctl_tcp_notsent_lowat parameter. This issue arises from improper synchronization mechanisms when multiple threads attempt to access and modify the same kernel memory location simultaneously. The sysctl_tcp_notsent_lowat parameter controls the minimum number of bytes that must remain in the send buffer before the kernel considers a connection to be in a "not sent" state, which directly impacts TCP flow control and network performance characteristics. The vulnerability stems from the kernel's failure to properly protect against concurrent access patterns that can lead to inconsistent or corrupted data reads.
The technical flaw manifests as a classic race condition where the kernel's TCP subsystem allows simultaneous read and write operations to the sysctl_tcp_notsent_lowat variable without adequate synchronization primitives. When one thread attempts to read this value while another thread modifies it, the reader may observe an inconsistent state or partial updates, leading to unpredictable behavior in TCP connection handling. This data-race condition specifically affects the kernel's network stack operations and can result in incorrect flow control decisions that impact network throughput and connection reliability. The vulnerability is categorized under CWE-362, which identifies race conditions as a fundamental weakness in concurrent programming that can lead to security and stability issues.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromise network security and system stability. When the data-race occurs during TCP connection management, it can cause connections to behave unpredictably, leading to potential denial of service conditions or data corruption in network communications. Network applications relying on consistent TCP behavior may experience unexpected connection drops, packet loss, or throughput anomalies that can be exploited by malicious actors to disrupt services or gain unauthorized access to network resources. The vulnerability particularly affects systems handling high volumes of concurrent TCP connections where the likelihood of encountering the race condition increases significantly.
Mitigation strategies for CVE-2022-49587 require immediate kernel updates that implement proper read synchronization using the READ_ONCE() macro as specified in the fix. System administrators should prioritize patching affected systems with the latest kernel versions containing the fix, which typically involves applying the specific commit that adds the READ_ONCE() wrapper around the sysctl_tcp_notsent_lowat parameter access. Organizations should also implement monitoring solutions to detect unusual network behavior patterns that might indicate the vulnerability's exploitation, particularly in environments with high TCP connection volumes. Additionally, security teams should review their network monitoring configurations to ensure they can detect anomalous TCP behavior that might result from this race condition, as the vulnerability can manifest through subtle network performance degradation rather than obvious system crashes or security breaches. The fix aligns with ATT&CK technique T1499.004, which involves network disruption through system resource exhaustion or manipulation of network parameters, making it a critical vulnerability for enterprise security teams to address promptly.