CVE-2026-80630
CriticalCVSS 9.8Exploitation Probability (EPSS)
Low risk42th percentile - higher than 42% of all known CVEs
Summary
In the Linux kernel, the net/sched/sch_fq_codel module has a vulnerability where qdisc_tree_reduce_backlog is called during peek before restoring the qlen counter. This can lead to incorrect deactivation of the parent class and, consequently, to a wild memory access in the qfq scheduler, manifesting as a general protection fault.
Risk Assessment
An attacker could exploit this vulnerability to cause a system crash (kernel panic) or potentially escalate privileges, posing a serious threat to system availability and integrity.
Recommendation
Immediately update the Linux kernel to a version containing the fix that moves the qdisc_tree_reduce_backlog call after restoring qlen. Also monitor distribution security advisories and apply the appropriate patches.
Other vulnerabilities in Linux kernel
See all- CVE-2026-98374Unknown
In the Linux kernel, a use-after-free vulnerability exists in tcp_send_synack() involving retransmit_skb_hint. When tcp_send_synack() replaces the cloned SYN skb at the head of the retransmit queue with a copy, it frees the original but tp->retransmit_skb_hint still points to the freed object, which can be exploited by an unprivileged TFO client to trigger a use-after-free.
- CVE-2026-98373Unknown
In the Linux kernel, a bug exists in move_hugetlb_page_tables() where the destination address is advanced too far when the source and destination offsets within their page tables differ. This can lead to a kernel panic on x86-64.
- CVE-2026-98048Unknown
In the Linux kernel's BPF subsystem, mark_fastcall_pattern_for_call() must ensure that a matched "spill; call; fill" instruction series is not interrupted by a jump. Otherwise the rewrite applied by bpf_remove_fastcall_spills_fills() is unsound. The fix records instructions targeted by jumps in insn_aux_data[*].jump_target and uses this flag to stop growing a pattern.
- CVE-2026-98047Unknown
In the Linux kernel's BPF subsystem, in_rbtree_lock_required_cb() only checks the innermost verifier frame, so rbtree callback restrictions disappear in a nested static subprogram call frame. The subprogram can unlock the tree, remove and drop the node being compared, then relock, leading to freed memory being linked into the tree.
- CVE-2026-98045Unknown
In the Linux kernel, a BPF verifier vulnerability affects stack helpers that may block on filesystem reads (e.g., resolving build IDs) but were not marked as sleepable. The verifier could still allow these helpers from non-sleepable regions such as RCU or preemption-disabled sections.
- CVE-2026-98044Unknown
In the Linux kernel, the BPF verifier mishandled legacy packet-load instructions (BPF_LD_ABS/BPF_LD_IND) reached from callbacks, triggering a verifier bug warning and an -EFAULT on BPF_PROG_LOAD. A privileged program loader could trigger this issue.
- CVE-2026-98043Unknown
In the Linux kernel, the BPF verifier incorrectly inferred that a pointer with an unbounded offset is non-NULL based solely on its type. As a result, a BPF program could pass verification while a NULL pointer dereference occurred at runtime.
- CVE-2026-98042Unknown
In the Linux kernel, the BPF verifier could resurrect a scalar id dropped by collect_linked_regs() because snapshots of compared registers were taken before linked registers were collected. This could lead to range inconsistencies and precision propagation issues.
- CVE-2026-98041High
In the Linux kernel, the BPF verifier incorrectly predicted the outcome of pointer vs zero comparisons in JMP32 instructions, failing to distinguish BPF_JMP from BPF_JMP32 comparisons. This led to incorrect inference that a jump is always taken.
- CVE-2026-98040Unknown
In the Linux kernel, the BPF verifier did not mark the zero register as precise for a register-form NULL check. As a result, one path was pruned and the program could dereference a zero pointer at runtime.
Original NVD description (English source)
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/
Vulnerability data from NVD (NIST) · CISA KEV · EPSS