CVE-2026-80978
Description
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.
How to fix
- Linux Linuxfb889a619723032140f5d983a3a34d25a5a2bed4, b160422f8103574425e2834130e169d84c94fa1d, d36e75f5669140b66515ad3a176ca6337bd80a5e, 84783961cb8bdb36b4f41a02ce43aafc6d52b176, bc4e05ae66c9797a0972ac44326e69c5305e0020, af0ee8f04bea22cdb331fa3509e17f81b48938ad, 9144f2c53a04465a6878172b523f640313c5559e, 6b222adeb9340306e2ff97127c76117abb9b3df8 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < fb889a619723032140f5d983a3a34d25a5a2bed4, 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < b160422f8103574425e2834130e169d84c94fa1d, 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < d36e75f5669140b66515ad3a176ca6337bd80a5e, 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < 84783961cb8bdb36b4f41a02ce43aafc6d52b176, 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < bc4e05ae66c9797a0972ac44326e69c5305e0020, 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < af0ee8f04bea22cdb331fa3509e17f81b48938ad, 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < 9144f2c53a04465a6878172b523f640313c5559e, 1a37e412a0225fcba5587f24c0dfc7636efc8b69 ≤ v < 6b222adeb9340306e2ff97127c76117abb9b3df8, 3.11 | fb889a619723032140f5d983a3a34d25a5a2bed4, b160422f8103574425e2834130e169d84c94fa1d, d36e75f5669140b66515ad3a176ca6337bd80a5e, 84783961cb8bdb36b4f41a02ce43aafc6d52b176, bc4e05ae66c9797a0972ac44326e69c5305e0020, af0ee8f04bea22cdb331fa3509e17f81b48938ad, 9144f2c53a04465a6878172b523f640313c5559e, 6b222adeb9340306e2ff97127c76117abb9b3df8 |
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