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CVE-2026-53011
net/sched: taprio: fix use-after-free in advance_sched() on schedule switch
Published 2026-06-24 (4 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-2026-53011 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
In advance_sched(), when should_change_schedules() returns true, switch_schedules() is called to promote the admin schedule to oper. switch_schedules() queues the old oper schedule for RCU freeing via call_rcu(), but 'next' still points into an entry of the old oper schedule. The subsequent 'next->end_time = end_time' and rcu_assign_pointer(q->current_entry, next) are use-after-free. Fix this by selecting 'next' from the new oper schedule immediately after switch_schedules(), and using its pre-calculated end_time. setup_first_end_time() sets the first entry's end_time to base_time + interval when the schedule is installed, so the value is already correct. The deleted 'end_time = sched_base_time(admin)' assignment was also harmful independently: it would overwrite the new first entry's pre-calculated end_time with just base_time.
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
- 2026-06-24 (4 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.0% 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 |
|---|---|---|
| 5.2 | 5.10.258 | a8fc396519ef |
| 5.2 | 5.15.209 | 347187457816 |
| 5.2 | 6.1.175 | 7256996e1ef5 |
| 5.2 | 6.6.141 | eee072fe16c6 |
| 5.2 | 6.12.91 | 1bd286fa3e21 |
| 5.2 | 6.18.33 | b73235da5dde |
| 5.2 | 7.0.10 | 0e62171df8ed |
| 5.2 | 7.1 | 105425b1969c |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | tracker |
| DLA-4664-1 | 2026-07-03 | bullseye 5.10.259-1 | 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:LAttack vector, local
- The vulnerable taprio schedule switch is reached through local `NETLINK_ROUTE`/tc qdisc configuration, not by unauthenticated network packets. An attacker sends `RTM_NEWQDISC` messages to install and later switch taprio schedules.
- AC:LAttack complexity, low
- The trigger is deterministic once the attacker installs an oper schedule and a later admin schedule with chosen base times/intervals. The attacker controls the schedule timing, so no condition beyond attacker control is required.
- PR:LPrivileges required, low
- The rtnetlink qdisc path requires `CAP_NET_ADMIN` in the target network namespace. Because tc/qdisc configuration is reachable with namespaced `CAP_NET_ADMIN` via user namespaces in reasonable deployments, this is low privilege rather than high privilege.
- UI:NUser interaction, none
- No victim action is required after the attacker can issue the local netlink configuration. The hrtimer-driven schedule transition occurs automatically.
- S:UScope, unchanged
- The vulnerability corrupts kernel memory within the same kernel security authority. It is a standard local kernel privilege-escalation/DoS class issue, not a VM or hardware boundary escape.
- C:HConfidentiality impact, high
- This is a use-after-free of taprio schedule entry memory that leaves `current_entry` pointing into freed objects. As a kernel UAF, it can plausibly be shaped into memory disclosure primitives.
- I:HIntegrity impact, high
- The stale schedule entry is later written and used by scheduler/dequeue paths, giving attacker-influenced heap corruption potential. Under the required kernel guidance, a UAF is high integrity impact because it can be leveraged for arbitrary write or control-flow compromise.
- A:HAvailability impact, high
- The dangling schedule entry can be dereferenced after RCU freeing by the timer or dequeue path. Even without full exploitation, this can cause kernel oops, panic, or repeated crashes.