# CVE-2024-40981: batman-adv: bypass empty buckets in batadv_purge_orig_ref() > A flaw in the Linux kernel's batman-adv module causes soft lockups, leading to denial of service by stalling CPU execution. - **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 12 Jul 2024 - **Updated:** 11 May 2026 - **Also known as:** BELL-CVE-2024-40981, DEBIAN-CVE-2024-40981, GHSA-66mx-vw67-wmq9, UBUNTU-CVE-2024-40981 ## What is CVE-2024-40981? CVE-2024-40981 is a medium-severity denial of service vulnerability in Linux kernel, published on 12 Jul 2024. It can only be exploited from the same machine or local network, with no action from the victim. ### Official description In the Linux kernel, the following vulnerability has been resolved: batman-adv: bypass empty buckets in batadv_purge_orig_ref() Many syzbot reports are pointing to soft lockups in batadv_purge_orig_ref() [1] Root cause is unknown, but we can avoid spending too much time there and perhaps get more interesting reports. [1] watchdog: BUG: soft lockup - CPU#0 stuck for 27s! [kworker/u4:6:621] Modules linked in: irq event stamp: 6182794 hardirqs last enabled at (6182793): [] __local_bh_enable_ip+0x224/0x44c kernel/softirq.c:386 hardirqs last disabled at (6182794): [] __el1_irq arch/arm64/kernel/entry-common.c:533 [inline] hardirqs last disabled at (6182794): [] el1_interrupt+0x24/0x68 arch/arm64/kernel/entry-common.c:551 softirqs last enabled at (6182792): [] spin_unlock_bh include/linux/spinlock.h:396 [inline] softirqs last enabled at (6182792): [] batadv_purge_orig_ref+0x114c/0x1228 net/batman-adv/originator.c:1287 softirqs last disabled at (6182790): [] spin_lock_bh include/linux/spinlock.h:356 [inline] softirqs last disabled at (6182790): [] batadv_purge_orig_ref+0x164/0x1228 net/batman-adv/originator.c:1271 CPU: 0 PID: 621 Comm: kworker/u4:6 Not tainted 6.8.0-rc7-syzkaller-g707081b61156 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024 Workqueue: bat_events batadv_purge_orig pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : should_resched arch/arm64/include/asm/preempt.h:79 [inline] pc : __local_bh_enable_ip+0x228/0x44c kernel/softirq.c:388 lr : __local_bh_enable_ip+0x224/0x44c kernel/softirq.c:386 sp : ffff800099007970 x29: ffff800099007980 x28: 1fffe00018fce1bd x27: dfff800000000000 x26: ffff0000d2620008 x25: ffff0000c7e70de8 x24: 0000000000000001 x23: 1fffe00018e57781 x22: dfff800000000000 x21: ffff80008aab71c4 x20: ffff0001b40136c0 x19: ffff0000c72bbc08 x18: 1fffe0001a817bb0 x17: ffff800125414000 x16: ffff80008032116c x15: 0000000000000001 x14: 1fffe0001ee9d610 x13: 0000000000000000 x12: 0000000000000003 x11: 0000000000000000 x10: 0000000000ff0100 x9 : 0000000000000000 x8 : 00000000005e5789 x7 : ffff80008aab61dc x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000 x2 : 0000000000000006 x1 : 0000000000000080 x0 : ffff800125414000 Call trace: __daif_local_irq_enable arch/arm64/include/asm/irqflags.h:27 [inline] arch_local_irq_enable arch/arm64/include/asm/irqflags.h:49 [inline] __local_bh_enable_ip+0x228/0x44c kernel/softirq.c:386 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline] _raw_spin_unlock_bh+0x3c/0x4c kernel/locking/spinlock.c:210 spin_unlock_bh include/linux/spinlock.h:396 [inline] batadv_purge_orig_ref+0x114c/0x1228 net/batman-adv/originator.c:1287 batadv_purge_orig+0x20/0x70 net/batman-adv/originator.c:1300 process_one_work+0x694/0x1204 kernel/workqueue.c:2633 process_scheduled_works kernel/workqueue.c:2706 [inline] worker_thread+0x938/0xef4 kernel/workqueue.c:2787 kthread+0x288/0x310 kernel/kthread.c:388 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.8.0-rc7-syzkaller-g707081b61156 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024 pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : arch_local_irq_enable+0x8/0xc arch/arm64/include/asm/irqflags.h:51 lr : default_idle_call+0xf8/0x128 kernel/sched/idle.c:103 sp : ffff800093a17d30 x29: ffff800093a17d30 x28: dfff800000000000 x27: 1ffff00012742fb4 x26: ffff80008ec9d000 x25: 0000000000000000 x24: 0000000000000002 x23: 1ffff00011d93a74 x22: ffff80008ec9d3a0 x21: 0000000000000000 x20: ffff0000c19dbc00 x19: ffff8000802d0fd8 x18: 1fffe00036804396 x17: ffff80008ec9d000 x16: ffff8000802d089c x15: 0000000000000001 ---truncated--- Weakness: CWE-667 (Improper Locking) ## Which versions are affected by CVE-2024-40981? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2024-40981? Apply the vendor's patch. ## Is CVE-2024-40981 being exploited? There is no known exploitation of CVE-2024-40981 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2024-40981 and fix it if it is affected. What it is: CVE-2024-40981 is a medium-severity denial of service vulnerability in Linux kernel, published on 12 Jul 2024. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2024-40981 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2024-40981/ (Markdown: https://insights.sbomify.com/CVE-2024-40981/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2024-40981 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-40981 - OSV: https://osv.dev/vulnerability/CVE-2024-40981 --- From sbomify Insights: https://insights.sbomify.com/CVE-2024-40981/ Summaries are generated and may contain mistakes; the official description above is the record.