ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()
CVE-2026-89561 · published 11 Sept 2026
How serious is it
- Severity: high, CVSS score 7.5 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-89561?
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Who is affected
- Linux Linux: 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 62b63a505c10e8db76017ef73c0b243e0dc5d288, 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < e7123e10c86eb88eaa90537dd1f232706de2d308, 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < 63f50e9f90d0287ad66a0955ebfc2d3a9c044a1c, 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 to < eab3a917cdcb182542a3aac6a0d2d30659ca9821
- Linux Linux: 5.7
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
In the Linux kernel, the following vulnerability has been resolved:
ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()
ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL
check when reading idev->cnf.rpl_seg_enabled.
When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears
dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev
check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with
dev->ip6_ptr already NULL.
Reproduced by flooding the receiving interface with ping6 traffic while
flapping its MTU between 1500 and 1200:
BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070
Read of size 4 at addr 00000000000006b4 by task ping6/394
CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full)
Call Trace:
<IRQ>
kasan_report+0xc6/0x100
ipv6_rpl_srh_rcv+0xb3/0x1070
ip6_protocol_deliver_rcu+0x759/0x9a0
ip6_input_finish+0xa8/0x1b0
ip6_input+0xe1/0x490
ipv6_rcv+0x33d/0x460
__netif_receive_skb_one_core+0xd6/0x130
process_backlog+0x2cc/0xa00
__napi_poll.constprop.0+0x56/0x270
net_rx_action+0x327/0x730
handle_softirqs+0x11e/0x630
do_softirq+0xb3/0xf0
</IRQ>
Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from
ipv6_rthdr_rcv(), which already has an idev lookup.
Fix the NULL dereference on the RPL path by checking idev in
ipv6_rthdr_rcv(), before it calls either function. The callees take idev as
an argument and no longer call __in6_dev_get(), so the packet is now
dropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths.
Check your whole app
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References
- git.kernel.org/stable/c/62b63a505c10e8db76017ef73c0b243e0dc5d288
- git.kernel.org/stable/c/e7123e10c86eb88eaa90537dd1f232706de2d308
- git.kernel.org/stable/c/63f50e9f90d0287ad66a0955ebfc2d3a9c044a1c
- git.kernel.org/stable/c/eab3a917cdcb182542a3aac6a0d2d30659ca9821
- git.kernel.org/stable/c/f826df95332c07380206dbd54178b6eefb311aba
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON