ip: orphan prefetched skbs before multicast forwarding
CVE-2026-89564 · published 11 Sept 2026
How serious is it
- Severity: high, CVSS score 7.8 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-2026-89564?
Paste this prompt into Claude Code, Cursor or any AI coding tool: it runs a free Shippable scan of your project and fixes what it finds. Built with Lovable, Bolt or v0? Scan your live app. Or upload your package file.
Who is affected
- Linux Linux: cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449 to < 882212d317a7c16ab70d20656f6b1c42abada9f6, cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449 to < e62aef7d6a5b27569bf540bbe11a9482117ff588, cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449 to < a8af6fbac895f057c4b8ff8a2e3fb4c5827fe4ce, cf7fbe660f2dbd738ab58aea8e9b0ca6ad232449 to < f1281d4b99089fbaf0d3579bba62a814ebb4de4d
- 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:
ip: orphan prefetched skbs before multicast forwarding
IPv4 and IPv6 input preserve an skb->sk association installed by
bpf_sk_assign() so that local delivery can use the selected socket under
RCU. Both address families can also prefetch a socket in UDP early demux.
In both paths (BPF and UDP early demux) a reference is not guaranteed to
be held on the socket.
When a multicast packet is not locally deliverable, IPv6 hands the
original skb to ip6_mr_input(). IPv4's ip_mr_input() similarly keeps the
original skb when local delivery is not needed. Either path can put the
skb on an unresolved multicast route queue or forward it after the
receive-side RCU section ends.
After the prefetched socket is destroyed, a later skb free invokes
sock_pfree() and dereferences the stale skb->sk. Orphan the skb before
each non-local multicast forwarding path. Local delivery retains the
original skb; the existing skb_clone() calls provide multicast forwarding
with a socket-free clone.
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/882212d317a7c16ab70d20656f6b1c42abada9f6
- git.kernel.org/stable/c/e62aef7d6a5b27569bf540bbe11a9482117ff588
- git.kernel.org/stable/c/a8af6fbac895f057c4b8ff8a2e3fb4c5827fe4ce
- git.kernel.org/stable/c/f1281d4b99089fbaf0d3579bba62a814ebb4de4d
- git.kernel.org/stable/c/e36ce6e78fe3fc3c071a26750783b7ba081ce10d
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON