# CVE-2026-64451: linux: In the Linux kernel, the following vulnerability has been resolved:  tracing: Fix NULL pointer dereference in func_se...

CVE-2026-64451 is fixed in linux on 1 platform by DEBIAN-CVE-2026-64451 (version 7.1.4-1), released August 7, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-64451
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0014
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 25, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 14 | 7.1.4-1 | [DEBIAN-CVE-2026-64451](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64451.md) | Aug 7, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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