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CVE-2026-72035
net/sched: sch_taprio: Replace direct dequeue call with peek and qdisc_dequeue_peeked
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/sched. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72035 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When taprio's software path peeks a non-work-conserving child qdisc, the child stashes the peeked skb in its gso_skb; taprio_dequeue_from_txq() then takes the packet with a direct child ->dequeue() call, which ignores that stash, orphans the peeked skb and desyncs the child's qlen/backlog. With a qfq child this re-enters the child on an emptied list and dereferences NULL, panicking the kernel from softirq on ordinary egress. Take the packet through qdisc_dequeue_peeked(), as sch_red and sch_sfb now do. The helper returns the child's stashed skb first and is a no-op when there is none, so a work-conserving child is unaffected and the gated path now consumes the skb whose length was charged to the budget.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/sched/sch_taprio.c
- What this is
- CBS/ETF/TAPRIO QDISCSMAINTAINERS section matched on net/sched/sch_taprio.c · netdev@vger.kernel.org · Maintained
- Kernel module
- sch_taprio
Check it on the machine
grep -w CONFIG_NET_SCH_TAPRIO /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w sch_taprioPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_NET_SCH_TAPRIO
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 8.2 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.59%, higher than 47.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/sched
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.20 | 5.10.266 | 51f8af240aed |
| 4.20 | 5.15.217 | 17ab5f76f389 |
| 4.20 | 6.1.184 | f60d5c12e055 |
| 4.20 | 6.6.145 | 6ee5a7665a90 |
| 4.20 | 6.12.97 | 18d580cb00c5 |
| 4.20 | 6.18.40 | e2b7ee61989f |
| 4.20 | 7.1.5 | 2dcebbd1ad2e |
| 4.20 | 7.2 | e056e1dfcddc |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:NAttack vector, network
- The fault is in taprio's software egress dequeue path (`__dev_queue_xmit` → `__qdisc_run` → `taprio_dequeue` → `taprio_dequeue_from_txq`) during ordinary packet transmission in softirq; on TSN/automotive/industrial gateways where taprio+qfq is already deployed, any remote peer can trigger it by sending traffic that causes egress through the gated queues.
- AC:LAttack complexity, low
- Once taprio is configured with a non-work-conserving child such as qfq on the software path (no full offload, TXTIME_ASSIST disabled), peek followed by the incorrect direct `dequeue()` deterministically orphans the stashed skb, desyncs qlen/backlog, and re-enters qfq on an emptied list; the attacker fully controls triggering traffic with no uncontrollable races.
- PR:NPrivileges required, none
- Installing taprio and grafting a qfq child requires CAP_NET_ADMIN via RTM_NEWQDISC, but on reasonably deployed TSN/industrial systems where operators have already configured this stack, triggering the bug requires only the ability to send packets through the affected interface—no credentials or capabilities on the victim host.
- UI:NUser interaction, none
- Exploitation needs only attacker-generated network traffic (or any local sender) once the qdisc hierarchy exists; no victim login, mount, file open, or other interactive action is required at trigger time.
- S:UScope, unchanged
- The NULL dereference kernel panic and qdisc qlen/backlog corruption occur entirely within the host kernel's security authority; this is not a VM escape, container breakout, or IOMMU/DMA boundary bypass.
- C:NConfidentiality impact, none
- The published failure mode is a NULL pointer dereference in qfq after taprio mishandles the peek stash; although the peeked skb is orphaned and child counters desync, there is no use-after-free, out-of-bounds read, or demonstrated arbitrary kernel memory disclosure primitive.
- I:LIntegrity impact, low
- Calling `child->ops->dequeue()` instead of `qdisc_dequeue_peeked()` orphans the peek-stashed skb and corrupts the child qdisc's qlen/backlog accounting before the fatal qfq re-entry, enabling attacker-driven mis-accounting of queued traffic on the affected egress path prior to panic.
- A:HAvailability impact, high
- With a qfq child the desynchronized dequeue path dereferences NULL from softirq during ordinary egress, panicking the kernel; the condition is repeatable whenever gated transmission exercises the peek/dequeue mismatch, causing total host availability loss.