CVE-2026-98625 from a local attacker's viewpoint
CVE-2026-98625 from a local attacker's viewpoint The attacker starts with local influence CVE-2026-98625 is a local-use-after-free in the Linux netfilter flowtable offload code. Ubuntu records low privileges required, high attack complexity, present attack requirements, and no user interaction. The issue is not reached by sending a single malformed packet from the internet. An attacker needs…
CVE-2026-98625 is a local use-after-free vulnerability found in the Linux netfilter flowtable offload code. This issue requires local access to exploit, as an attacker must first gain enough control over the network and flow lifecycle to influence the relevant components. The race condition occurs when a network worker publishes the dead state of a flow but fails to clear the pending bit in time.
If the worker is preempted at this stage, an RCU callback may free the flow before the worker resumes, leading to the exposure of freed memory.
The fix for this vulnerability postpones the publication of the flow state until after the worker has completed its cleanup and a memory barrier has been triggered. This ensures that the flow state transition matches the destroy lifecycle, preventing the memory corruption that can result from the uaf bug.
Local attackers, such as those with elevated privileges on a shared system or those who can influence the network configuration, may find it easier to exploit this vulnerability due to their ability to create and destroy offloaded flows. However, remote attackers are limited by their lack of local control over the network and flow lifecycle.
The primary risk associated with this vulnerability is memory corruption, which can lead to unpredictable system behavior. While the sources do not provide a proof-of-concept or evidence of active exploitation, the potential impact on affected systems is deemed high. Systems that delegate network configuration to less trusted workloads, such as shared network testbeds, multi-tenant gateways, and appliance platforms with many local control paths, may be particularly vulnerable.
Detecting this vulnerability can be challenging, as kernel crashes and memory corruption may not always be directly linked to CVE-2026-98625. Investigative measures include monitoring for unusual local networking control activity, repeated flow teardown, kernel memory safety reports, and crashes on susceptible builds. To mitigate the risk, it is recommended to apply the patch for the affected kernels and verify the running release.
Reducing local exposure and unnecessary offload workloads can also help minimize the attack surface until a verified kernel state is achieved.
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