CVE-2026-98968: Linux kernel · amt: send the relay's General Query directly from the receive path
Source GCVE Database
Not known to be exploited · CVSS 8.1 High · fixed in e7183b7d518ce8b3e1f7284f9881d7a87569df14 : patch Linux kernel soon.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.4% chance of exploitation in 30 days – higher than 42% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in e7183b7d518ce8b3e1f7284f9881d7a87569df14, e7ea63b4195a150604993044ab574d8240f2a399, afae89de73dd693cfa329580ba0fba63bd3f0a11 +2
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 23 Oct 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– |
Description
In the Linux kernel, the following vulnerability has been resolved: amt: send the relay's General Query directly from the receive path An skb queued in a qdisc can outlive the tunnel it references through a raw pointer in skb->cb. For example, with igmp_qrv set to 1 on the relay a tunnel lives for 135s, so a netem delay of 180s on the amt device outlives it; when the tunnel expires and is freed, the subsequent dequeue triggers a use-after-free in amt_dev_xmit(). BUG: KASAN: slab-use-after-free in amt_dev_xmit+0x2763/0x2e20 Call Trace: amt_dev_xmit+0x2763/0x2e20 [drivers/net/amt.c:1262] dev_hard_start_xmit+0x22f/0x620 sch_direct_xmit+0x12e/0xac0 netem_dequeue+0x333/0xc50 net_tx_action+0x35c/0xa60 amt_send_igmp_gq() and amt_send_mld_gq() are only called from amt_request_handler(), inside the rcu_read_lock_bh() section of amt_rcv(). amt_request_handler() already has the tunnel the query is for: it found or created it inside that section. Queuing the query with dev_queue_xmit() only leads back into amt_dev_xmit(), which strips the Ethernet header and calls amt_send_membership_query() for that tunnel. Make that call directly from the two senders instead, the same way amt_send_advertisement() transmits from the receive path. The query never waits in a qdisc, the tunnel is only dereferenced inside the RCU section that found or created it, and nothing is stored in skb->cb, so no lookup or refcount is needed. Remove the query branch of amt_dev_xmit(), amt_skb_cb() and struct amt_skb_cb, which have no users left. Behaviour changes: - The relay's own General Queries no longer pass through the amt device's egress path: its qdisc, tc egress (clsact/tcx), the netfilter egress hook and packet taps. They are still visible as UDP on the underlay. - A query that is sent successfully is no longer counted as tx_dropped. The old query branch left through the unlock label, which counted every sent query as dropped. - A query that reaches amt_dev_xmit() on a relay from elsewhere, such as a userspace querier, is now dropped at the IGMP/MLD type switch. Before, it trusted whatever skb->cb held, and a NULL tunnel hit the WARN_ON(1).
References
- nvd.nist.gov/vuln/detail/CVE-2026-98968 (opens in a new tab)
- git.kernel.org/stable/c/181cb48c1e9af6b402567e132f879f89d1c54131 (opens in a new tab)
- git.kernel.org/stable/c/95114e421196250e3d9662f12df442799477d3c3 (opens in a new tab)
- git.kernel.org/stable/c/afae89de73dd693cfa329580ba0fba63bd3f0a11 (opens in a new tab)
- git.kernel.org/stable/c/e7183b7d518ce8b3e1f7284f9881d7a87569df14 (opens in a new tab)
- git.kernel.org/stable/c/e7ea63b4195a150604993044ab574d8240f2a399 (opens in a new tab)