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CVE-2026-90160

lwt_bpf: Restore reserved headroom after xmit program

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.110, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

In the Linux kernel, the following vulnerability has been resolved: lwt_bpf: Restore reserved headroom after xmit program ip_finish_output2() expands an skb to LL_RESERVED_SPACE(dev) before LWT xmit. An LWT_XMIT BPF program can then modify the skb head and still return BPF_OK, so bpf_xmit() rechecks the remaining headroom before the skb continues to neighbour output. That recheck uses dst->dev->hard_header_len. This is not enough for the neighbour cached-header path: neigh_hh_output() copies the cached hardware header using the aligned hh_cache size, HH_DATA_MOD for short headers or HH_DATA_ALIGN(hh_len) otherwise. On Ethernet, hard_header_len is 14 but the cached copy needs 16 bytes. If an LWT_XMIT BPF program calls bpf_skb_change_head(skb, 1, 0), the skb can still have 15 bytes of headroom after the program. The existing check accepts that, after which neigh_hh_output() hits its headroom warning and drops the skb. Use LL_RESERVED_SPACE(dst->dev) in the post-BPF headroom check to match the reservation made before LWT xmit.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in 753e5cdcca5474d230d62bb3489e5168ab27c272; From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in c488071c3441fa34f5a87cd6c12ce2cc6304f20e; From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in a38c0eb447e2dd0120a2ebcdba470f9505ac8907; From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in de2b2004e16f2930eb689175e2c1998b0a68d499; From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in 7d043e24520a273c362be5dd7d9c82796879a49b; From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in 7cf561843ed0ad57501892a65abb77957e6c800f; From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in 179a5b2171573d94a25c9aa8e1c9f9ac352ad316; From 3a0af8fd61f90920f6fa04e4f1e9a6a73c1b4fd2 · fixed in 5fe7007aed9ad069b2bd77e5d0c875c64f5c0269

  • Linux Linux

    4.10

  • KernelLinux

    From 4.10.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 8

git.kernel.org