CVE-2026-80978 in Linux
Riassunto
di MITRE • 12/09/2026
In the Linux kernel, the following vulnerability has been resolved:
net: cap advertised IP tunnel headroom
IP tunnel devices derive their advertised needed_headroom from lower output devices. A stack of user-created devices can make the derived value larger than the 16-bit skb header offsets can represent. Once IP output reserves it, skb head expansion can wrap those offsets.
The runtime transmit path already caps a growing needed_headroom at 512. Apply the same cap when tunnel configuration publishes needed_headroom derived from a lower output device.
Capping the advertised value is safe: IP tunnel transmit still expands the skb when a packet needs more headroom. A nonsensical stacked configuration can therefore incur an extra reallocation, but it cannot publish an unbounded reservation to upper layers.
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