CVE-2026-80630

Received Received - Intake

Memory Corruption in Linux Kernel Traffic Control

Publication date: 2026-08-28

Last updated on: 2026-08-29

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: net/sched: sch_fq_codel: Do not call qdisc_tree_reduce_backlog during peek before restoring qlen Whenever fq_codel drops packets during peek, it calls qdisc_tree_reduce_backlog. An issue arises because it calls qdisc_tree_reduce_backlog before it reincrements the qlen. If qlen drops to zero, but peek returns an skb, the parent's qlen_notify callback will be executed even though fq_codel still has 1 packet on the queue and, thus, will mistakenly deactivate the parent's class causing issues like a recent report [1] and a wild memory access in qfq: [ 29.371146][ T360] Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI [ 29.371666][ T360] KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127] [ 29.371987][ T360] CPU: 6 UID: 0 PID: 360 Comm: tc Not tainted 7.1.0-rc5-00285-gc530e5b2dbc6-dirty #82 PREEMPT(full) [ 29.372384][ T360] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 29.372620][ T360] RIP: 0010:qfq_deactivate_agg (include/linux/list.h:1029 (discriminator 2) include/linux/list.h:1043 (discriminator 2) net/sched/sch_qfq.c:1369 (discriminator 2) net/sched/sch_qfq.c:1395 (discriminator 2)) sch_qfq [ 29.373544][ T360] RSP: 0018:ffff888102417370 EFLAGS: 00010216 [ 29.373800][ T360] RAX: 0000000000000000 RBX: ffff88811224d568 RCX: dffffc0000000000 [ 29.374079][ T360] RDX: 1ffff11021fe1543 RSI: ffff88810ff0aa00 RDI: dffffc0000000000 [ 29.374368][ T360] RBP: ffff88811224c280 R08: dead000000000122 R09: 1bd5a00000000024 [ 29.374649][ T360] R10: fffffbfff7940329 R11: fffffbfff7940329 R12: 0000000000000000 [ 29.374926][ T360] R13: dead000000000100 R14: ffff88811224d580 R15: ffff88811224d578 [ 29.375207][ T360] FS: 00007f5b794e5780(0000) GS:ffff88815d1e9000(0000) knlGS:0000000000000000 [ 29.375545][ T360] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 29.375823][ T360] CR2: 000055ffb091f000 CR3: 000000010a305000 CR4: 0000000000750ef0 [ 29.376103][ T360] PKRU: 55555554 [ 29.376258][ T360] Call Trace: [ 29.376401][ T360] <TASK> ... [ 29.376885][ T360] qfq_reset_qdisc (net/sched/sch_qfq.c:357 net/sched/sch_qfq.c:1487) sch_qfq [ 29.377074][ T360] qdisc_reset (net/sched/sch_generic.c:1057) [ 29.377414][ T360] __qdisc_destroy (net/sched/sch_generic.c:1096) [ 29.377600][ T360] qdisc_graft (net/sched/sch_api.c:1062 net/sched/sch_api.c:1053 net/sched/sch_api.c:1159) [ 29.378593][ T360] tc_get_qdisc (net/sched/sch_api.c:1528 net/sched/sch_api.c:1556) Fix this by only calling qdisc_tree_reduce_backlog in peek after the qlen is restored. [1] http://lore.kernel.org/netdev/CAN2cbVe79oj0O9==m4+4x3v+O+qzRagA=2=wkrp9i9=CqYvyZA@mail.gmail.com/

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-08-28

Last Modified

2026-08-29

Generated

2026-09-18

AI Q&A

2026-08-28

EPSS Evaluated

2026-09-15

NVD

CVE-2026-80630

EUVD

EUVD-2026-67506

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	7.1.0-rc5-00285-gc530e5b2dbc6-dirty
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves the fq_codel network scheduler. When it drops packets during a peek operation, it incorrectly calls qdisc_tree_reduce_backlog before restoring the queue length (qlen). This can cause the parent queue to mistakenly deactivate, leading to issues like crashes or memory access errors.

Detection Guidance

This vulnerability is specific to the Linux kernel's fq_codel and qfq packet scheduling mechanisms. Detection requires checking kernel logs for general protection faults or wild memory access errors related to these modules. Monitor system logs for crashes or errors involving sch_qfq or sch_fq_codel.

Impact Analysis

This vulnerability can cause system crashes, kernel panics, or wild memory access errors, potentially leading to denial of service or data corruption. It affects network traffic management in Linux systems using the fq_codel scheduler.

Compliance Impact

This vulnerability is a Linux kernel network stack issue causing memory corruption and crashes. It does not directly impact data privacy or security controls required by GDPR or HIPAA. Compliance risks would arise only if exploitation led to system instability or unauthorized access, which is not indicated in the provided details.

Mitigation Strategies

Apply the latest Linux kernel patches that address this issue. Update your system to a kernel version that includes the fix for CVE-2026-80630. If immediate patching is not possible, consider disabling or reconfiguring fq_codel and qfq packet scheduling to avoid triggering the vulnerable code paths.

Hi! I’m here to help you understand CVE-2026-80630. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70