CVE-2026-89951
HighCVSS 8.8Summary
In the Linux kernel batman-adv module, fragment reassembly reuses the skb from the highest-numbered buffered fragment, and if the interface it was received on is deleted before the chain completes, the merged packet can re-enter the receive path with a stale skb->dev and skb_iif. This can lead to use of a freed net_device. The fix refreshes the receive device metadata before running packet handlers.
Risk Assessment
The vulnerability can lead to a use-after-free and potential kernel code execution or system crash. It affects systems using batman-adv mesh networking.
Recommendation
Update the Linux kernel to a version containing the fix that refreshes receive device metadata for merged fragments. Avoid deleting network interfaces during active mesh traffic if updating is not possible.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: batman-adv: fix stale receive device on merged fragments Fragment reassembly reuses the skb from the highest-numbered buffered fragment as the merged packet. When that fragment was received on a hard interface which is deleted before the chain completes, the merged skb can re-enter the receive path with a stale skb->dev and skb_iif. batadv_batman_skb_recv() passes such merged packets through the normal receive handlers again. DAT and bridge loop avoidance both derive the ARP header length from skb->dev, so they can dereference the freed net_device before the packet reaches the local mesh interface. Refresh the receive device metadata from the current receive device before running the packet handlers. This keeps internally reinjected merged fragments consistent with the normal receive path after hard interface teardown.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS