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CVE-2026-64114
ipv4: raw: reject IP_HDRINCL packets with ihl < 5
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/ipv4. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64114 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/ipv4/raw.c
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on net/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_INET /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sidy
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switch
- CONFIG_INET
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-19 (3 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.14%, higher than 2.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ipv4
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.12 | 5.10.258 | 1065b9efa412 |
| 2.6.12 | 5.15.209 | bc20dbd48c26 |
| 2.6.12 | 6.1.175 | 5a564f737ec5 |
| 2.6.12 | 6.6.142 | 3c5411fa4944 |
| 2.6.12 | 6.12.92 | 145e9afa5b90 |
| 2.6.12 | 6.18.34 | 7725cd3b4717 |
| 2.6.12 | 7.0.11 | bbe0be67de29 |
| 2.6.12 | 7.1 | 915fab69823a |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- Exploitation requires local syscalls (socket/sendmsg on a raw IP_HDRINCL socket); malformed packets are injected locally into the output path, not via remote network ingress which validates ihl >= 5.
- AC:LAttack complexity, low
- The attacker fully controls the crafted header ihl value and can install the required xfrm AH policy and route via CAP_NET_ADMIN in their own network namespace, making exploitation reliable without conditions outside attacker control.
- PR:LPrivileges required, low
- Triggering requires CAP_NET_RAW for raw sockets and CAP_NET_ADMIN to install xfrm AH policy, both obtainable by an unprivileged user via user+network namespaces or a container granted NET_ADMIN without init-namespace root.
- UI:NUser interaction, none
- No victim interaction is required; the attacker sends the malformed packet directly through their own raw socket and configured IPsec policy.
- S:UScope, unchanged
- Impact is kernel memory corruption and panic within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.
- C:HConfidentiality impact, high
- The integer underflow in ah_output() memcpy length produces an out-of-bounds read of near SIZE_MAX bytes, providing an arbitrary kernel memory read primitive beyond any bounded disclosure.
- I:HIntegrity impact, high
- The same memcpy with underflowed length causes a massive out-of-bounds write that can corrupt adjacent kernel heap memory and be leveraged for control-flow hijacking.
- A:HAvailability impact, high
- The OOB memcpy reliably causes a kernel-mode fault and host panic, as reproduced with KASAN and in a rootless Docker container, denying all system availability.