CVE-2026-98570
Description
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: keep room for the mac header in dst_dev_overhead() The seg6, ioam6 and rpl lwtunnels size their skb_cow_head() request as the length they are about to push plus dst_dev_overhead(), then push the new headers and rebuild the mac header below them with skb_mac_header_rebuild(). That rebuild needs skb->mac_len of headroom, but dst_dev_overhead() leaves LL_RESERVED_SPACE() of the egress device, 16 bytes for plain Ethernet. Where the mac header is longer than that, as it is on ingress through a VLAN device with reorder_hdr off, the rebuild runs out of room: skb_set_mac_header(skb, -skb->mac_len) computes a negative offset, stores it unchecked in the u16 skb->mac_header, and the memmove that follows writes skb->mac_len bytes about 64 KB past skb->head. Forwarding plain ping6 traffic through such a device reproduces it on all five seg6 encapsulation modes and on the rpl and ioam6 inline paths; skb->mac_header comes back as 65534 on a 704-byte head. Return the larger of the two. The helper already returns skb->mac_len when it has no dst, so this only makes the other branch agree, and it covers every caller rather than each call site in turn.
How to fix
- Linux Linux36c07127924f11fc5741a780abcaaf808fe9ef13, 87cd6b717e4069dca34e0866e57eaeb44d3b173e, 6.13, 6.14, 5.16, 6.2, 6.7, 5.11 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | dce525185bc92864e5a318040285ee070563fe34 ≤ v < 36c07127924f11fc5741a780abcaaf808fe9ef13, dce525185bc92864e5a318040285ee070563fe34 ≤ v < 87cd6b717e4069dca34e0866e57eaeb44d3b173e, 8471e228448a818e4c27cab4b681b2e758e46cf5, c432cd18a07b623651ed15ea167bd303467004cc, 634710a372ba65bee667c2f6e58a97658c639eab, c447c5a9c47bb4858ab12bf90879fe595d2b7f46, ab9de9c48316d2622d3bf353916b99971570e2c9, 2fcc9f3798ef82399564d247458e69abd10e683b, 371d8dc298b4f59e99b4564ac5d906fce0932c69, b26f015dfb07b6be12d005a0ed0c5c43b7bedbf3, c0b11dc50590e10590b39dcda79835cd32f49d00, 4c12c3c8abd8b888945d31e7bdbb0d8b73032fc5, 25d8e065c7972dc98fd7a4cac322d5367eaede88, 4a855c5aec41bf84922224ab7a74e088776e3ac4, a9f0407414e16176fdbbbd298c9e18d6dfdf96bc, 6.12.16 ≤ v < 6.13, 6.13.4 ≤ v < 6.14, 5.15.179 ≤ v < 5.16, 6.1.130 ≤ v < 6.2, 6.6.81 ≤ v < 6.7, 5.10.235 ≤ v < 5.11, 6.14 | 36c07127924f11fc5741a780abcaaf808fe9ef13, 87cd6b717e4069dca34e0866e57eaeb44d3b173e, 6.13, 6.14, 5.16, 6.2, 6.7, 5.11 |
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