CVE-2026-68338: Linux kernel · net/packet: avoid fanout hook re-registration after unregister
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 7.8 High · fixed in c820f4b7f2fa38f8769db0d0cefdd94e2721504d : patch Linux kernel soon.
Data as of 26 Oct 2026, 13:47 UTC
- EPSS
- 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Total control over the software or total information disclosure
CISA SSVC assessment, 2026-10-16.
- Patch
- Available – fixed in c820f4b7f2fa38f8769db0d0cefdd94e2721504d, acb40ebfa5c4d62f84339fcbf713f2a9fd033a71, a885387dae7986a55bae5c77a15bdd447f64e9b9 +5
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 10 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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| LinuxLinux | Affected
| Fixed in
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Description
In the Linux kernel, the following vulnerability has been resolved: net/packet: avoid fanout hook re-registration after unregister packet_set_ring() temporarily detaches a socket from packet delivery while reconfiguring its ring. It records the previous running state, clears po->num, unregisters the protocol hook when needed, drops po->bind_lock, and later restores po->num and re-registers the hook from the saved was_running value. That unlocked window can race with NETDEV_UNREGISTER. The notifier can observe the socket as not running, skip __unregister_prot_hook(), and invalidate the per-socket binding by setting po->ifindex to -1 and clearing po->prot_hook.dev. A one-member fanout group can still retain its shared fanout hook device pointer. When packet_set_ring() resumes, re-registering solely from the stale was_running state can re-add the fanout hook after the device has been unregistered. Treat po->ifindex == -1 as an invalidated binding after reacquiring po->bind_lock. This is distinct from ifindex 0, the normal unbound/wildcard state: ifindex -1 marks an existing device binding that was invalidated when the device was unregistered. Restore po->num as before, but do not re-register the hook if device unregister already detached the socket.
References
- git.kernel.org/stable/c/acb40ebfa5c4d62f84339fcbf713f2a9fd033a71 (opens in a new tab)
- git.kernel.org/stable/c/c820f4b7f2fa38f8769db0d0cefdd94e2721504d (opens in a new tab)
- git.kernel.org/stable/c/4628efbdc7affd094181f5263e65c1062e31f15f (opens in a new tab)
- git.kernel.org/stable/c/80ec024d53a05c60ad1d08968dcf745f10c1665c (opens in a new tab)
- git.kernel.org/stable/c/0a052e0808e015e68144a9877e6ef42b952c49fa (opens in a new tab)
- git.kernel.org/stable/c/1bc55c29cd85818e9052f17deb287d5a11fb817f (opens in a new tab)
- git.kernel.org/stable/c/a885387dae7986a55bae5c77a15bdd447f64e9b9 (opens in a new tab)
- git.kernel.org/stable/c/50aff80475abd3533eef4320477037e6fcc6b56e (opens in a new tab)