CVE-2026-98570 net: ipv6: keep room for the mac header in dst_dev_overhead()
A memory corruption vulnerability in the Linux kernel IPv6 stack allows remote attackers to cause denial of service or execute code via crafted network traffic.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98570?
CVE-2026-98570 is a memory corruption vulnerability in Linux, published on 18 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
net: ipv6: keep room for the mac header in dst_dev_overhead()
The seg6, ioam6 and rpl lwtunnels size their skb_cow_head() request as the length they are about to push plus dst_dev_overhead(), then push the new headers and rebuild the mac header below them with skb_mac_header_rebuild(). That rebuild needs skb->mac_len of headroom, but dst_dev_overhead() leaves LL_RESERVED_SPACE() of the egress device, 16 bytes for plain Ethernet.
Where the mac header is longer than that, as it is on ingress through a VLAN device with reorder_hdr off, the rebuild runs out of room: skb_set_mac_header(skb, -skb->mac_len) computes a negative offset, stores it unchecked in the u16 skb->mac_header, and the memmove that follows writes skb->mac_len bytes about 64 KB past skb->head. Forwarding plain ping6 traffic through such a device reproduces it on all five seg6 encapsulation modes and on the rpl and ioam6 inline paths; skb->mac_header comes back as 65534 on a 704-byte head.
Return the larger of the two. The helper already returns skb->mac_len when it has no dst, so this only makes the other branch agree, and it covers every caller rather than each call site in turn.
Which versions are affected by CVE-2026-98570?
How do I fix CVE-2026-98570?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-98570 being exploited?
There is no known exploitation of CVE-2026-98570 in the wild and no public exploit code.
Sources
Also known as AZL-109086, BELL-CVE-2026-98570, DEBIAN-CVE-2026-98570, GHSA-4prh-wfp5-28j7, UBUNTU-CVE-2026-98570.