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CVE-2026-64116
ipv6: ioam: add NULL check for idev in ipv6_hop_ioam()
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem net/ipv6. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64116 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
Reported by Sashiko: The function ipv6_hop_ioam() accesses __in6_dev_get(skb->dev)->cnf.ioam6_enabled without validating the returned idev pointer. Because addrconf_ifdown() can concurrently clear dev->ip6_ptr via RCU, __in6_dev_get() can return NULL during interface teardown, which could cause a NULL pointer dereference when processing an IOAM Hop-by-Hop option. Let's add a check and use SKB_DROP_REASON_IPV6DISABLED accordingly.
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/ipv6/exthdrs.c
- What this is
- NETWORKING [IPv4/IPv6]MAINTAINERS section matched on net/ipv6/exthdrs.c · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -w CONFIG_IPV6 /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_IPV6
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
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.51%, higher than 42.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/ipv6
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.15 | 5.15.210 | c7e8971abd70 |
| 5.15 | 6.1.176 | 09cbfd4b81ae |
| 5.15 | 6.6.143 | 1dca7e491f07 |
| 5.15 | 6.12.92 | 902daac307eb |
| 5.15 | 6.18.34 | abdd03229414 |
| 5.15 | 7.0.11 | cf75eb661704 |
| 5.15 | 7.1 | d4ea0dfd7501 |
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:NAttack vector, network
- The bug is in the IPv6 receive path (ipv6_rcv → ip6_rcv_core → ipv6_parse_hopopts → ipv6_hop_ioam), triggered by a remotely deliverable IPv6 packet with a Hop-by-Hop IOAM option.
- AC:LAttack complexity, low
- An attacker can reliably win the TOCTOU race by flooding IOAM Hop-by-Hop packets while concurrently unregistering the netdev (e.g., via user namespace with CAP_NET_ADMIN and `ip link del`), controlling both sides of the race.
- PR:NPrivileges required, none
- No kernel privileges are required to send crafted IPv6 packets; interface unregister also occurs during normal container/pod lifecycle on shared cloud hosts without attacker admin action.
- UI:NUser interaction, none
- Exploitation requires only sending network packets during interface teardown and does not depend on any victim user action.
- S:UScope, unchanged
- Impact is a kernel NULL dereference and crash on the receiving host; it does not cross a VM, container, or IOMMU security boundary.
- C:NConfidentiality impact, none
- The fault is a NULL pointer read at a fixed offset (idev->cnf.ioam6_enabled), causing an immediate page fault with no controlled or bounded information disclosure.
- I:NIntegrity impact, none
- This is a read-side NULL dereference only; there is no memory corruption, arbitrary write, or code execution primitive.
- A:HAvailability impact, high
- A successful trigger causes a kernel NULL pointer dereference, producing an oops or panic and denying service on the affected system.