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CVE-2025-40042: tracing: Fix race condition in kprobe initialization causing NULL pointer dereference

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix race condition in kprobe initialization causing NULL pointer dereference There is a critical race condition in kprobe initialization that can lead to NULL pointer dereference and kernel crash. [1135630.084782] Unable to handle kernel paging request at virtual address 0000710a04630000 ... [1135630.260314] pstate: 404003c9 (nZcv DAIF +PAN -UAO) [1135630.269239] pc : kprobe_perf_func+0x30/0x260 [1135630.277643] lr : kprobe_dispatcher+0x44/0x60 [1135630.286041] sp : ffffaeff4977fa40 [1135630.293441] x29: ffffaeff4977fa40 x28: ffffaf015340e400 [1135630.302837] x27: 0000000000000000 x26: 0000000000000000 [1135630.312257] x25: ffffaf029ed108a8 x24: ffffaf015340e528 [1135630.321705] x23: ffffaeff4977fc50 x22: ffffaeff4977fc50 [1135630.331154] x21: 0000000000000000 x20: ffffaeff4977fc50 [1135630.340586] x19: ffffaf015340e400 x18: 0000000000000000 [1135630.349985] x17: 0000000000000000 x16: 0000000000000000 [1135630.359285] x15: 0000000000000000 x14: 0000000000000000 [1135630.368445] x13: 0000000000000000 x12: 0000000000000000 [1135630.377473] x11: 0000000000000000 x10: 0000000000000000 [1135630.386411] x9 : 0000000000000000 x8 : 0000000000000000 [1135630.395252] x7 : 0000000000000000 x6 : 0000000000000000 [1135630.403963] x5 : 0000000000000000 x4 : 0000000000000000 [1135630.412545] x3 : 0000710a04630000 x2 : 0000000000000006 [1135630.421021] x1 : ffffaeff4977fc50 x0 : 0000710a04630000 [1135630.429410] Call trace: [1135630.434828] kprobe_perf_func+0x30/0x260 [1135630.441661] kprobe_dispatcher+0x44/0x60 [1135630.448396] aggr_pre_handler+0x70/0xc8 [1135630.454959] kprobe_breakpoint_handler+0x140/0x1e0 [1135630.462435] brk_handler+0xbc/0xd8 [1135630.468437] do_debug_exception+0x84/0x138 [1135630.475074] el1_dbg+0x18/0x8c [1135630.480582] security_file_permission+0x0/0xd0 [1135630.487426] vfs_write+0x70/0x1c0 [1135630.493059] ksys_write+0x5c/0xc8 [1135630.498638] __arm64_sys_write+0x24/0x30 [1135630.504821] el0_svc_common+0x78/0x130 [1135630.510838] el0_svc_handler+0x38/0x78 [1135630.516834] el0_svc+0x8/0x1b0 kernel/trace/trace_kprobe.c: 1308 0xffff3df8995039ec <kprobe_perf_func+0x2c>: ldr x21, [x24,#120] include/linux/compiler.h: 294 0xffff3df8995039f0 <kprobe_perf_func+0x30>: ldr x1, [x21,x0] kernel/trace/trace_kprobe.c 1308: head = this_cpu_ptr(call->perf_events); 1309: if (hlist_empty(head)) 1310: return 0; crash> struct trace_event_call -o struct trace_event_call { ... [120] struct hlist_head *perf_events; //(call->perf_event) ... } crash> struct trace_event_call ffffaf015340e528 struct trace_event_call { ... perf_events = 0xffff0ad5fa89f088, //this value is correct, but x21 = 0 ... } Race Condition Analysis: The race occurs between kprobe activation and perf_events initialization: CPU0 CPU1 ==== ==== perf_kprobe_init perf_trace_event_init tp_event->perf_events = list;(1) tp_event->class->reg (2)← KPROBE ACTIVE Debug exception triggers ... kprobe_dispatcher kprobe_perf_func (tk->tp.flags & TP_FLAG_PROFILE) head = this_cpu_ptr(call->perf_events)(3) (perf_events is still NULL) Problem: 1. CPU0 executes (1) assigning tp_event->perf_events = list 2. CPU0 executes (2) enabling kprobe functionality via class->reg() 3. CPU1 triggers and reaches kprobe_dispatcher 4. CPU1 checks TP_FLAG_PROFILE - condition passes (step 2 completed) 5. CPU1 calls kprobe_perf_func() and crashes at (3) because call->perf_events is still NULL CPU1 sees that kprobe functionality is enabled but does not see that perf_events has been assigned. Add pairing read an ---truncated---

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2025-40042 is a Linux kernel flaw that can crash a system during kprobe tracing setup. The issue is a timing race: tracing can become active before related perf event data is safely visible. The documented impact is availability loss, not data theft or privilege escalation.

Executive priority

Treat this as an availability risk for Linux infrastructure, especially heavily instrumented production systems. Patch through normal kernel maintenance unless vendor guidance or local crash evidence raises urgency.

Technical view

The race occurs between perf_kprobe_init/perf_trace_event_init and kprobe dispatch. CPU1 can enter kprobe_perf_func after TP_FLAG_PROFILE is observed but before call->perf_events is visible, causing a NULL pointer dereference at this_cpu_ptr(call->perf_events) and a kernel crash.

Likely exposure

Exposure is likely on Linux systems running affected kernel versions with vulnerable kprobe/perf tracing code. Practical exposure depends on kernel branch, distributor backports, and whether tracing or perf-based kprobe functionality is used or reachable.

Exploitation context

The source bundle does not show CISA KEV listing, public exploitation, CVSS scoring, or attacker prerequisites. Evidence supports a race-triggered kernel crash scenario, but not remote exploitation, privilege escalation, or active abuse.

Researcher notes

The bundle identifies a memory-ordering race in kprobe initialization and references multiple stable kernel commits. It does not provide complete version-range semantics, CVSS, exploitation evidence, or downstream distribution package status.

Mitigation direction

  • Update to a Linux kernel containing the referenced stable fix commits.
  • Check distribution advisories for backported fixes matching your kernel package.
  • Prioritize systems using kprobes, perf tracing, observability agents, or kernel instrumentation.
  • If patch timing is unclear, monitor vendor guidance before changing tracing configuration.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, containers hosts, and cloud images.
  • Compare running kernels against vendor advisories and the referenced stable commits.
  • Review observability and performance tooling for kprobe or perf tracing usage.
  • Check crash logs for kprobe_perf_func or trace_kprobe NULL dereference signatures.
Prepared
Confidence
medium
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2025-40042 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
9Source links

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux50d780560785b068c358675c5f0bf6c83b5c373e, 50d780560785b068c358675c5f0bf6c83b5c373e, 50d780560785b068c358675c5f0bf6c83b5c373e, 50d780560785b068c358675c5f0bf6c83b5c373e, 50d780560785b068c358675c5f0bf6c83b5c373e, 50d780560785b068c358675c5f0bf6c83b5c373e, 50d780560785b068c358675c5f0bf6c83b5c373e, 50d780560785b068c358675c5f0bf6c83b5c373eunaffected
LinuxLinux2.6.33, 0, 5.4.301, 5.10.246, 5.15.195, 6.1.157, 6.6.113, 6.12.54, 6.17.3, 6.18affected
Weakness

CWE details

No CWE listed

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