CVE-2026-43496: Linux kernel · net/sched: sch_red: Replace direct dequeue call with peek and qdisc_dequeue_peeked
Affects Linux kernelSource CVE Database V5
Not known to be exploited · fixed in ce051eede433f876d322ac3550a36a3c6fc4c231 : update Linux kernel when convenient.
Data as of 6 Nov 2026, 16:04 UTC
Rated by Threat Radar · No CVSS score from NVD or the CNA
Thin evidence
One scorer or none- 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
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-11-06.
- Patch
- Available – fixed in ce051eede433f876d322ac3550a36a3c6fc4c231, c7335f4dc0fa21f7015b910c6fc2f4d599732328, 587dcf970a525f543d8b5855d9f37a4ca97b76ef +5
Exploitation evidence
Disclosed: evidence found.
CVE published 21 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 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/sched: sch_red: Replace direct dequeue call with peek and qdisc_dequeue_peeked When red qdisc has children (eg qfq qdisc) whose peek() callback is qdisc_peek_dequeued(), we could get a kernel panic. When the parent of such qdiscs (eg illustrated in patch #3 as tbf) wants to retrieve an skb from its child (red in this case), it will do the following: 1a. do a peek() - and when sensing there's an skb the child can offer, then - the child in this case(red) calls its child's (qfq) peek. qfq does the right thing and will return the gso_skb queue packet. Note: if there wasnt a gso_skb entry then qfq will store it there. 1b. invoke a dequeue() on the child (red). And herein lies the problem. - red will call the child's dequeue() which will essentially just try to grab something of qfq's queue. [ 78.667668][ T363] KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f] [ 78.667927][ T363] CPU: 1 UID: 0 PID: 363 Comm: ping Not tainted 7.1.0-rc1-00033-g46f74a3f7d57-dirty #790 PREEMPT(full) [ 78.668263][ T363] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 78.668486][ T363] RIP: 0010:qfq_dequeue+0x446/0xc90 [sch_qfq] [ 78.668718][ T363] Code: 54 c0 e8 dd 90 00 f1 48 c7 c7 e0 03 54 c0 48 89 de e8 ce 90 00 f1 48 8d 7b 48 b8 ff ff 37 00 48 89 fa 48 c1 e0 2a 48 c1 ea 03 <80> 3c 02 00 74 05 e8 ef a1 e1 f1 48 8b 7b 48 48 8d 54 24 58 48 8d [ 78.669312][ T363] RSP: 0018:ffff88810de573e0 EFLAGS: 00010216 [ 78.669533][ T363] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 78.669790][ T363] RDX: 0000000000000009 RSI: 0000000000000004 RDI: 0000000000000048 [ 78.670044][ T363] RBP: ffff888110dc4000 R08: ffffffffb1b0885a R09: fffffbfff6ba9078 [ 78.670297][ T363] R10: 0000000000000003 R11: ffff888110e31c80 R12: 0000001880000000 [ 78.670560][ T363] R13: ffff888110dc4150 R14: ffff888110dc42b8 R15: 0000000000000200 [ 78.670814][ T363] FS: 00007f66a8f09c40(0000) GS:ffff888163428000(0000) knlGS:0000000000000000 [ 78.671110][ T363] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 78.671324][ T363] CR2: 000055db4c6a30a8 CR3: 000000010da67000 CR4: 0000000000750ef0 [ 78.671585][ T363] PKRU: 55555554 [ 78.671713][ T363] Call Trace: [ 78.671843][ T363] <TASK> [ 78.671936][ T363] ? __pfx_qfq_dequeue+0x10/0x10 [sch_qfq] [ 78.672148][ T363] ? __pfx__printk+0x10/0x10 [ 78.672322][ T363] ? srso_alias_return_thunk+0x5/0xfbef5 [ 78.672496][ T363] ? lockdep_hardirqs_on_prepare+0xa8/0x1a0 [ 78.672706][ T363] ? srso_alias_return_thunk+0x5/0xfbef5 [ 78.672875][ T363] ? trace_hardirqs_on+0x19/0x1a0 [ 78.673047][ T363] red_dequeue+0x65/0x270 [sch_red] [ 78.673217][ T363] ? srso_alias_return_thunk+0x5/0xfbef5 [ 78.673385][ T363] tbf_dequeue.cold+0xb0/0x70c [sch_tbf] [ 78.673566][ T363] __qdisc_run+0x169/0x1900 The right thing to do in #1b is to grab the skb off gso_skb queue. This patchset fixes that issue by changing #1b to use qdisc_dequeue_peeked() method instead.
References
- git.kernel.org/stable/c/03b0aaeba082ae981a0dfe96cdd03d02050537a1 (opens in a new tab)
- git.kernel.org/stable/c/c7335f4dc0fa21f7015b910c6fc2f4d599732328 (opens in a new tab)
- git.kernel.org/stable/c/45cd83c5c470ba49fe261489c8358ad7b9df7c45 (opens in a new tab)
- git.kernel.org/stable/c/36aa34f42cb6842cf371f3a2d3e855d24fd57a50 (opens in a new tab)
- git.kernel.org/stable/c/ce051eede433f876d322ac3550a36a3c6fc4c231 (opens in a new tab)
- git.kernel.org/stable/c/8d09618840b99ef00154d3e731ce9b11e096196d (opens in a new tab)
- git.kernel.org/stable/c/587dcf970a525f543d8b5855d9f37a4ca97b76ef (opens in a new tab)
- git.kernel.org/stable/c/458d5615272d3de535748342eb68ca492343048c (opens in a new tab)
- cert-portal.siemens.com/productcert/html/ssa-784472.html (opens in a new tab)