ip6mr: do not clone dst in ip6mr_cache_report()
CVE-2026-90111 · published 17 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-2026-90111?
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Who is affected
- Linux Linux: 67f415dd29063a5906c560051c00e42dcf01a4dd to < 7f8287f606c8c028d4224e85d95dc448c6d6d623, 67f415dd29063a5906c560051c00e42dcf01a4dd to < 42ef371466d5648f5c9e8bc219f0af0a2c2bbf8c, 67f415dd29063a5906c560051c00e42dcf01a4dd to < f57b0fd1c62e1be274ee154ab7fb8ac4481b7f89, 67f415dd29063a5906c560051c00e42dcf01a4dd to < 4a674afaae4136c71943aa3e35d433676fd40e8f
- Linux Linux: 5.3
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:
ip6mr: do not clone dst in ip6mr_cache_report()
IPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU.
When an ingress multicast packet misses MFC lookup,
ip6mr_cache_unresolved() places the skb onto the unresolved queue,
escaping the receive-side RCU grace period.
If the underlying route is deleted and freed, and the MFC queue is later
resolved with a wrong parent interface, ip6_mr_forward() invokes
ip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes
dst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab
use-after-free.
Report packets queued to mroute6_sk (a raw socket) and netlink
notifications do not require an attached dst entry.
Fix this by:
1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs
do not hold a dst.
2. Dropping skb_dst before queuing unresolved skbs in
ip6mr_cache_unresolved(), matching the fact that multicast
forwarding resolves outgoing routes anew via ip6_route_output().
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/7f8287f606c8c028d4224e85d95dc448c6d6d623
- git.kernel.org/stable/c/42ef371466d5648f5c9e8bc219f0af0a2c2bbf8c
- git.kernel.org/stable/c/f57b0fd1c62e1be274ee154ab7fb8ac4481b7f89
- git.kernel.org/stable/c/4a674afaae4136c71943aa3e35d433676fd40e8f
- git.kernel.org/stable/c/235b42b5860189eb8c27c36435ad932cae65a734
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON