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CVE-2026-68127
ila: reload IPv6 header after pskb_may_pull in checksum adjust
Published 2026-08-10 (2 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-2026-68127 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ila_csum_adjust_transport() caches ip6h = ipv6_hdr(skb) before calling pskb_may_pull(). On a non-linear skb whose transport header sits in a page fragment, pskb_may_pull() can call __pskb_pull_tail() / pskb_expand_head() and free the old skb head, leaving ip6h dangling; the following get_csum_diff(ip6h, p) then reads freed memory. ila_update_ipv6_locator() uses ip6h (and the iaddr derived from it) again after the csum-adjust call and additionally writes the new locator through that pointer. Impact: a remote IPv6 packet routed through a configured ILA csum-adjust-transport route or receive-side mapping triggers a slab-use-after-free in ila_update_ipv6_locator() (KASAN). The route or mapping requires CAP_NET_ADMIN to configure, but trigger packets are unauthenticated once it exists. Reload ip6h after each pskb_may_pull() in ila_csum_adjust_transport() before the csum-diff read. In ila_update_ipv6_locator() only the ILA_CSUM_ADJUST_TRANSPORT case pulls the skb, so reload ip6h and iaddr in that case alone before the destination-address write; the neutral-map modes never pull and keep their cached pointers.
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/ila/ila_common.c
- What this is
- NETWORKING [GENERAL]MAINTAINERS section matched on net/ · netdev@vger.kernel.org · Maintained
- Kernel module
- ila
Check it on the machine
grep -w CONFIG_IPV6_ILA /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.
lsmod | grep -w ilaPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_IPV6_ILA
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
- 2026-08-10 (2 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.54%, higher than 44.0% 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 |
|---|---|---|
| 4.5 | 5.10.265 | e451a904606c |
| 4.5 | 5.15.216 | 1eadcb43893b |
| 4.5 | 6.1.183 | ba353caafb06 |
| 4.5 | 6.6.148 | 896a9512d0d8 |
| 4.5 | 6.12.101 | 7097a0280b17 |
| 4.5 | 6.18.42 | 472aba2603ca |
| 4.5 | 7.1.6 | c6a13ae00dab |
| 4.5 | 7.2 | 92d3817649df |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | tracker |
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 reached from ipv6_rcv() through NF_INET_PRE_ROUTING (ila_nf_input) or IPv6 routing/LWT input/output when remote IPv6 packets matching a configured ILA csum-adjust-transport mapping or route are processed; no local syscall is required on internet-facing routers, gateways, or NVO3/overlay hosts.
- AC:LAttack complexity, low
- Once ILA csum-adjust-transport is configured, a remote attacker can reliably send IPv6 TCP/UDP/ICMPv6 packets whose transport headers live in skb page fragments so pskb_may_pull() reallocates the head; they control packet layout and can retry without races or uncontrollable memory layout.
- PR:NPrivileges required, none
- Trigger packets are processed unauthenticated on the network datapath; although ILA routes/mappings require CAP_NET_ADMIN to install, that is operator infrastructure (also obtainable in a user netns), not a privilege the remote attacker needs to send the malformed IPv6 packets that hit ila_update_ipv6_locator().
- UI:NUser interaction, none
- No victim user action is required beyond normal IPv6 packet delivery; exploitation is fully automated once the affected ILA configuration exists and the attacker sends crafted packets to the host.
- S:UScope, unchanged
- The slab use-after-free corrupts kernel packet-processing memory within the host kernel security authority; it is not a VM escape, container breakout, or IOMMU/DMA boundary bypass.
- C:HConfidentiality impact, high
- ila_csum_adjust_transport() reads the cached IPv6 header via get_csum_diff(ip6h, p) after pskb_may_pull() frees the old skb head, causing a slab use-after-free read of freed memory that can disclose kernel heap contents.
- I:HIntegrity impact, high
- ila_update_ipv6_locator() then writes iaddr->loc = p->locator through the same stale iaddr pointer derived from the freed header, giving a slab use-after-free write primitive that can be leveraged for arbitrary memory corruption and control-flow hijacking.
- A:HAvailability impact, high
- The freed skb-head slab use-after-free was reproduced under KASAN and can cause kernel oops/panic during IPv6 receive/forwarding; even unsuccessful exploitation typically crashes or destabilizes the host.