CVE-2026-23379
Medium · 5.5CVSS
5.5
EPSS
0.1%
Published
Mar 25, 2026
CISA due date
—
Cloudanix analysis
A flaw in how the Linux kernel handles certain network traffic settings can let a logged-in user crash the whole machine by accident or on purpose.
- Exploitation
- Local Privilege
- Attacker needs
- Low Privilege
- Complexity
- Low
- Impact
- Denial Of Service
- Component
- OS kernel
- Class
- Improper Input Validation
- Remediation
- Patch
- Effort
- Medium
- Patch risk
- Low
What it actually does
Integer overflow in 32-bit q_sum and q_psum calculations within ets_offload_change allows division by zero when offloading ETS qdisc weights, triggering kernel oops and panic.
Why it matters to the business
Local configuration of ETS traffic shaping can crash the entire system, causing denial of service and unplanned downtime on affected Linux hosts.
How an attack unfolds
A local attacker invokes the tc utility to create or modify an ETS qdisc with offload enabled; crafted quantum values cause 32-bit summation to overflow to zero, resulting in a divide-by-zero fault during weight computation in the kernel scheduler.
How to fix it
Apply the upstream fix that changes q_sum and q_psum to 64-bit integers; rebuild and deploy updated kernel packages across all affected systems.
How to confirm the fix worked
Confirm the presence of the 64-bit integer change in ets_offload_change; attempt to reproduce the original tc command sequence and verify absence of divide error oops.
Typical attack path
- Obtain local shell access on a vulnerable Linux system
- Execute tc qdisc commands targeting sch_ets with offload parameters
- Supply quantum values that trigger 32-bit overflow in q_sum/q_psum
- Trigger division by zero in ets_offload_change leading to kernel panic
How to detect it
Search kernel logs and crash reports for oops or panic messages containing ets_offload_change, sch_ets, divide error, and the associated RIP offset; correlate with tc process invocations.
- ets_offload_change+0x11f/0x290 [sch_ets]
- Oops: divide error: 0000 [#1] SMP PTI
- Kernel panic - not syncing: Fatal exception
- Tainted: G E
- sch_ets(E)
What your security team should do
- Prioritize kernel updates on all production Linux systems using ETS qdisc offload
- Restrict unprivileged use of tc commands via SELinux or AppArmor policies where feasible
- Monitor for kernel oops reports involving sch_ets in centralized logging
- Test the fix in staging environments before broad rollout
The record
In the Linux kernel, the following vulnerability has been resolved: net/sched: ets: fix divide by zero in the offload path Offloading ETS requires computing each class' WRR weight: this is done by averaging over the sums of quanta as 'q_sum' and 'q_psum'. Using unsigned int, the same integer size as the individual DRR quanta, can overflow and even cause division by zero, like it happened in the following splat: Oops: divide error: 0000 [#1] SMP PTI CPU: 13 UID: 0 PID: 487 Comm: tc Tainted: G E 6.19.0-virtme #45 PREEMPT(full) Tainted: [E]=UNSIGNED_MODULE Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 RIP: 0010:ets_offload_change+0x11f/0x290 [sch_ets] Code: e4 45 31 ff eb 03 41 89 c7 41 89 cb 89 ce 83 f9 0f 0f 87 b7 00 00 00 45 8b 08 31 c0 45 01 cc 45 85 c9 74 09 41 6b c4 64 31 d2 <41> f7 f2 89 c2 44 29 fa 45 89 df 41 83 fb 0f 0f 87 c7 00 00 00 44 RSP: 0018:ffffd0a180d77588 EFLAGS: 00010246 RAX: 00000000ffffff38 RBX: ffff8d3d482ca000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffd0a180d77660 RBP: ffffd0a180d77690 R08: ffff8d3d482ca2d8 R09: 00000000fffffffe R10: 0000000000000000 R11: 0000000000000000 R12: 00000000fffffffe R13: ffff8d3d472f2000 R14: 0000000000000003 R15: 0000000000000000 FS: 00007f440b6c2740(0000) GS:ffff8d3dc9803000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000003cdd2000 CR3: 0000000007b58002 CR4: 0000000000172ef0 Call Trace: <TASK> ets_qdisc_change+0x870/0xf40 [sch_ets] qdisc_create+0x12b/0x540 tc_modify_qdisc+0x6d7/0xbd0 rtnetlink_rcv_msg+0x168/0x6b0 netlink_rcv_skb+0x5c/0x110 netlink_unicast+0x1d6/0x2b0 netlink_sendmsg+0x22e/0x470 ____sys_sendmsg+0x38a/0x3c0 ___sys_sendmsg+0x99/0xe0 __sys_sendmsg+0x8a/0xf0 do_syscall_64+0x111/0xf80 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f440b81c77e Code: 4d 89 d8 e8 d4 bc 00 00 4c 8b 5d f8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 11 c9 c3 0f 1f 80 00 00 00 00 48 8b 45 10 0f 05 <c9> c3 83 e2 39 83 fa 08 75 e7 e8 13 ff ff ff 0f 1f 00 f3 0f 1e fa RSP: 002b:00007fff951e4c10 EFLAGS: 00000202 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000481820 RCX: 00007f440b81c77e RDX: 0000000000000000 RSI: 00007fff951e4cd0 RDI: 0000000000000003 RBP: 00007fff951e4c20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 00007fff951f4fa8 R13: 00000000699ddede R14: 00007f440bb01000 R15: 0000000000486980 </TASK> Modules linked in: sch_ets(E) netdevsim(E) ---[ end trace 0000000000000000 ]--- RIP: 0010:ets_offload_change+0x11f/0x290 [sch_ets] Code: e4 45 31 ff eb 03 41 89 c7 41 89 cb 89 ce 83 f9 0f 0f 87 b7 00 00 00 45 8b 08 31 c0 45 01 cc 45 85 c9 74 09 41 6b c4 64 31 d2 <41> f7 f2 89 c2 44 29 fa 45 89 df 41 83 fb 0f 0f 87 c7 00 00 00 44 RSP: 0018:ffffd0a180d77588 EFLAGS: 00010246 RAX: 00000000ffffff38 RBX: ffff8d3d482ca000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffd0a180d77660 RBP: ffffd0a180d77690 R08: ffff8d3d482ca2d8 R09: 00000000fffffffe R10: 0000000000000000 R11: 0000000000000000 R12: 00000000fffffffe R13: ffff8d3d472f2000 R14: 0000000000000003 R15: 0000000000000000 FS: 00007f440b6c2740(0000) GS:ffff8d3dc9803000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000003cdd2000 CR3: 0000000007b58002 CR4: 0000000000172ef0 Kernel panic - not syncing: Fatal exception Kernel Offset: 0x30000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) ---[ end Kernel panic - not syncing: Fatal exception ]--- Fix this using 64-bit integers for 'q_sum' and 'q_psum'.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| openSUSE:Leap 16.0 | dtb-aarch64 | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-64kb | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-azure | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-default | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-default-base | 0 | 6.12.0-160000.27.1.160000.2.8 |
| openSUSE:Leap 16.0 | kernel-docs | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-kvmsmall | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-obs-build | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-obs-qa | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-rt | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-source | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-syms | 0 | 6.12.0-160000.28.1 |
| openSUSE:Leap 16.0 | kernel-zfcpdump | 0 | 6.12.0-160000.28.1 |
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