Security assessments indicate that CVE-2026-64451 presents a notable risk, potentially requiring prompt mitigation.
Status: Analyzed
Last updated: 🕒 03 Sep 2026, 15:29 UTC
Originally published on: 🕙 25 Jul 2026, 10:17 UTC
Time between publication and last update: 40 days
CVSS Release: version 3
nvd@nist.gov
Primary
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVE-2026-64451: In the Linux kernel, the following vulnerability has been resolved: tracing: Fix NULL pointer dereference in func_set_flag() func_set_flag() dereferences tr->current_trace_flags before verifying that the current tracer is actually the function tracer. When the active tracer has been switched away from "function" (e.g., to "wakeup_rt"), tr->current_trace_flags can be NULL, leading to a NULL pointer dereference and kernel crash. The call chain that triggers this is: trace_options_write() -> __set_tracer_option() -> trace->set_flag() /* func_set_flag */ In func_set_flag(), the first operation is: if (!!set == !!(tr->current_trace_flags->val & bit)) This dereferences tr->current_trace_flags unconditionally. The safety check that guards against a non-function tracer: if (tr->current_trace != &function_trace) return 0; is placed *after* the dereference, which is too late. This was observed with the following crash dump: BUG: unable to handle page fault at 0000000000000000 RIP: func_set_flag+0xd Call Trace: __set_tracer_option+0x27 trace_options_write+0x75 vfs_write+0x12a ksys_write+0x66 do_syscall_64+0x5b RIP: ffffffff914c973d RSP: ff67ec88b01dfdf0 RFLAGS: 00010202 RAX: 0000000000000000 RBX: ff3a826e80354580 RCX: 0000000000000001 RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffffffff93918080 The disassembly confirms the fault: func_set_flag+0: mov 0x1f08(%rdi), %rax ; RAX = tr->current_trace_flags = NULL func_set_flag+13: mov (%rax), %eax ; page fault: dereference NULL At the time of the crash: tr->current_trace_flags = 0x0 (NULL) tr->current_trace = wakeup_rt_tracer (not function_trace) The scenario is that a process opens a function tracer option file (such as "func_stack_trace"), then the current tracer is switched to another tracer (e.g., "wakeup_rt"), which sets current_trace_flags to NULL. When the process subsequently writes to the option file, func_set_flag() is invoked and crashes on the NULL dereference. Fix this by moving the current_trace check before the current_trace_flags dereference, so that func_set_flag() returns early when the function tracer is not active.
The exploitability of CVE-2026-64451 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).
CVE-2026-64451 presents an accessible attack vector with minimal effort required. Restricting access controls and implementing security updates are critical to reducing exploitation risks.
A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.
Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.
Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.
Above is the CVSS Sub-score Breakdown for CVE-2026-64451, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.
Below is the Impact Analysis for CVE-2026-64451, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.
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