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CVE PROGRAM SOURCE RECORD7.8 High

CVE-2026-64114

ipv4: raw: reject IP_HDRINCL packets with ihl < 5

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: ipv4: raw: reject IP_HDRINCL packets with ihl < 5 raw_send_hdrinc() validates that the caller-supplied IPv4 header fits within the message length: iphlen = iph->ihl * 4; err = -EINVAL; if (iphlen > length) goto error_free; if (iphlen >= sizeof(*iph)) { /* fix up saddr, tot_len, id, csum, transport_header */ } It does not, however, reject ihl < 5. For such a packet the "if (iphlen >= sizeof(*iph))" branch is skipped, leaving the crafted iphdr untouched, but the packet is still handed to __ip_local_out() and onward. Downstream consumers that read iph->ihl assume a sane value: net/ipv4/ah4.c:ah_output() in particular subtracts sizeof(struct iphdr) from top_iph->ihl * 4 and passes the (signed-int-negative, then cast to size_t) result to memcpy(), producing an OOB access of length close to SIZE_MAX and a host kernel panic. An IPv4 header with ihl < 5 is malformed by definition (RFC 791: "Internet Header Length is the length of the internet header in 32 bit words ... Note that the minimum value for a correct header is 5."). The kernel should not be willing to inject such a packet into its own output path. Reject "iphlen < sizeof(*iph)" alongside the existing "iphlen > length" check. This matches the principle that locally constructed packets that re-enter the IP stack must pass the same basic sanity tests that a foreign packet would be subjected to. Once this lands, the "if (iphlen >= sizeof(*iph))" wrapper around the fixup branch becomes redundant; left in place to keep the patch minimal and backport-friendly. A follow-up can unwrap it. Note that commit 86f4c90a1c5c ("ipv4, ipv6: ensure raw socket message is big enough to hold an IP header") ensures the message buffer is large enough to hold an iphdr, but does not constrain the self-reported iph->ihl. Reachability: the malformed packet source is any caller with CAP_NET_RAW, including an unprivileged process in a user+net namespace on a kernel with CONFIG_USER_NS=y. The reproduced AH crash also requires a matching xfrm AH policy on the outgoing route; a container granted CAP_NET_ADMIN can install that state and policy in its netns. Loopback bypasses xfrm_output, so the trigger uses a real netdev. Reproduced on UML + KASAN: kernel-mode fault at addr 0x0 with memcpy_orig at the crash site. Same shape reproduces inside a rootless Docker container with --cap-add NET_ADMIN on a stock distro kernel.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 1065b9efa4126df559b03a849c139ecfae92cd25affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < bc20dbd48c26e743f7e0845020c11ed2ce8b15eeaffected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 5a564f737ec54d63e8ee221d3ff396d07586d464affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 3c5411fa4944ed99af3d9d1de750ea8169b6dac9affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 145e9afa5b905229b4788bb72c3255f5a5f77508affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 7725cd3b471740fd23d25ed1da722c671fb2a5d3affected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < bbe0be67de296176e7243c76e3d9f02f6ae9ff0baffected
  • 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 915fab69823a14c170dbaa3b41978768e0fe62fcaffected

Linux Linux

Default version status: affected

  • 2.6.12affected
  • 0 to < 2.6.12unaffected
  • 5.10.258 to ≤ 5.10.*unaffected
  • 5.15.209 to ≤ 5.15.*unaffected
  • 6.1.175 to ≤ 6.1.*unaffected
  • 6.6.142 to ≤ 6.6.*unaffected
  • 6.12.92 to ≤ 6.12.*unaffected
  • 6.18.34 to ≤ 6.18.*unaffected
  • 7.0.11 to ≤ 7.0.*unaffected
  • 7.1 to ≤ *unaffected

References