CVE-2024-26759 is a race condition vulnerability in the Linux kernel's memory management subsystem, specifically within the swap cache handling code. The flaw occurs when multiple threads concurrently swap in the same swap entry under the SWP_SYNCHRONOUS_IO flag. In this scenario, two or more threads may allocate different pages (A and B) for the same swap entry and proceed with swap-in operations simultaneously. Due to a race, one thread (T1) may complete its swap-in first, free the swap entry, and then swap out a possibly modified page reusing the same swap entry. Meanwhile, another thread (T0) that started earlier but finished later installs a stale page (A) into the page table entry (PTE), bypassing the pte_same check because the PTE value appears unchanged. This results in data corruption and potential data loss. The issue is exacerbated in ZRAM devices, where swap_free() can discard the entry content, causing data loss even if the page was not modified. The vulnerability arises from an ABA problem in the swapcache management and improper synchronization between threads accessing the same swap entry. The fix involves reusing swapcache_prepare to pin the swap entry, ensuring only one thread can swap it in at a time and preventing parallel cache insertions. Threads that race wait in a loop with a short uninterruptible sleep to avoid livelock and excessive CPU usage. A reproducer demonstrates the vulnerability by spawning tens of thousands of threads swapping the same memory region, causing observable data loss every few minutes. The patch eliminates data loss with minimal performance overhead (~2% increase in swap-in latency). This vulnerability affects Linux kernel versions prior to the patch and is relevant to systems using swap, including those with ZRAM compressed swap devices. No known exploits are reported in the wild yet.

For European organizations, this vulnerability poses a significant risk to data integrity on Linux-based systems that utilize swap space, especially those employing ZRAM or other compressed swap devices. Data corruption or loss could affect critical applications relying on memory paging, such as database servers, virtualization hosts, and high-performance computing clusters. The race condition could lead to silent data corruption, making detection difficult and potentially causing application crashes, incorrect computations, or system instability. Organizations with large-scale Linux deployments, including cloud providers, financial institutions, research centers, and government agencies, could face operational disruptions and data integrity issues. The vulnerability does not directly enable privilege escalation or remote code execution but undermines system reliability and data correctness, which are critical for compliance with data protection regulations like GDPR. Additionally, the subtle nature of the bug may complicate forensic analysis and incident response. Systems under heavy multi-threaded load with frequent swapping are at higher risk. While no active exploitation is known, the vulnerability's presence in mainline Linux kernels and its reproducibility indicate a credible threat to data integrity in production environments.

European organizations should prioritize applying the official Linux kernel patch that addresses CVE-2024-26759 as soon as possible. Kernel updates from trusted Linux distributions (e.g., Debian, Ubuntu, Red Hat, SUSE) should be monitored and deployed promptly. For environments where immediate patching is not feasible, organizations can mitigate risk by reducing swap usage or disabling swap temporarily, especially on systems with high concurrency and swap activity. Monitoring tools should be enhanced to detect unusual swap-related errors or data corruption symptoms. Testing the patch in staging environments with workloads that heavily utilize swap can validate stability and performance impact before production rollout. For systems using ZRAM, verifying that the patched kernel version is deployed is critical due to the increased risk of data loss. Additionally, organizations should review multi-threaded applications that perform intensive memory operations and consider workload adjustments to minimize concurrent swap-in races. Backup and data integrity verification processes should be strengthened to detect and recover from potential silent data corruption. Finally, security teams should stay alert for any emerging exploit reports or proof-of-concept code that might appear in the wild.