CVE-2026-43086
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NULL Pointer Dereference in Linux Kernel IPVS

Publication date: 2026-05-06

Last updated on: 2026-05-06

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: ipvs: fix NULL deref in ip_vs_add_service error path When ip_vs_bind_scheduler() succeeds in ip_vs_add_service(), the local variable sched is set to NULL. If ip_vs_start_estimator() subsequently fails, the out_err cleanup calls ip_vs_unbind_scheduler(svc, sched) with sched == NULL. ip_vs_unbind_scheduler() passes the cur_sched NULL check (because svc->scheduler was set by the successful bind) but then dereferences the NULL sched parameter at sched->done_service, causing a kernel panic at offset 0x30 from NULL. Oops: general protection fault, [..] [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037] RIP: 0010:ip_vs_unbind_scheduler (net/netfilter/ipvs/ip_vs_sched.c:69) Call Trace: <TASK> ip_vs_add_service.isra.0 (net/netfilter/ipvs/ip_vs_ctl.c:1500) do_ip_vs_set_ctl (net/netfilter/ipvs/ip_vs_ctl.c:2809) nf_setsockopt (net/netfilter/nf_sockopt.c:102) [..] Fix by simply not clearing the local sched variable after a successful bind. ip_vs_unbind_scheduler() already detects whether a scheduler is installed via svc->scheduler, and keeping sched non-NULL ensures the error path passes the correct pointer to both ip_vs_unbind_scheduler() and ip_vs_scheduler_put(). While the bug is older, the problem popups in more recent kernels (6.2), when the new error path is taken after the ip_vs_start_estimator() call.
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Meta Information
Published
2026-05-06
Last Modified
2026-05-06
Generated
2026-05-07
AI Q&A
2026-05-06
EPSS Evaluated
N/A
NVD
CVE-2026-43086
EUVD
EUVD-2026-27582
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux_kernel linux_kernel From 6.2 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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AI Powered Q&A
How can this vulnerability impact me? :

This vulnerability can cause a kernel panic in affected Linux systems, leading to a system crash or denial of service. The NULL pointer dereference in the ipvs component can disrupt normal network service operations that rely on IP Virtual Server functionality.

Such a crash can result in downtime, loss of availability, and potential disruption of services running on the affected system.


Can you explain this vulnerability to me?

This vulnerability exists in the Linux kernel's IP Virtual Server (ipvs) component. Specifically, it involves a NULL pointer dereference in the error handling path of the ip_vs_add_service() function.

When ip_vs_bind_scheduler() succeeds, a local variable named sched is set to NULL. If a subsequent call to ip_vs_start_estimator() fails, the cleanup code calls ip_vs_unbind_scheduler() with sched still set to NULL. Although ip_vs_unbind_scheduler() checks if the scheduler is installed via svc->scheduler, it then dereferences the NULL sched pointer, causing a kernel panic due to a NULL pointer dereference.

The fix involves not clearing the sched variable after a successful bind, ensuring that the correct pointer is passed during cleanup and preventing the NULL dereference and kernel panic.


What immediate steps should I take to mitigate this vulnerability?

The vulnerability is fixed by ensuring that the local variable 'sched' is not cleared after a successful bind in the ip_vs_add_service() function. This prevents a NULL pointer dereference in the error path.

Immediate mitigation steps include updating your Linux kernel to a version that contains this fix, such as kernel version 6.2 or later where the error path handling has been corrected.


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