Linux Kernel up to 7.2.6/7.3-rc2 ftrace function_graph_enter_regs use after free

Summaryinfo

A vulnerability marked as very critical has been reported in Linux Kernel up to 7.2.6/7.3-rc2. This vulnerability affects the function function_graph_enter_regs of the component ftrace. The manipulation leads to use after free. This vulnerability is listed as CVE-2026-97937. The attack may be initiated remotely. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.6/7.3-rc2 and classified as very critical. This issue affects the function function_graph_enter_regs of the component ftrace. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: ftrace: fork: Initialize function graph state before copy_exec_state() dup_task_struct() copies the parent's task_struct, including ret_stack. ftrace_graph_init_task() clears the copied function graph state, but it currently runs after copy_exec_state(). For non-CLONE_VM forks, copy_exec_state() allocates a new task_exec_state. If that allocation fails, copy_process() reaches bad_fork_free and free_task() calls ftrace_graph_exit_task(). Since the child still carries the parent's ret_stack pointer, the unwind frees the parent's active function graph return stack. The parent subsequently accesses freed memory from function_graph_enter_regs(). KASAN reports: [ 22.190920] ================================================================== [ 22.195899] BUG: KASAN: slab-use-after-free in function_graph_enter_regs+0xa76/0xb90 [ 22.200747] Write of size 8 at addr ff110000054dc0a8 by task repro/1 [ 22.205134] [ 22.210770] CPU: 0 UID: 0 PID: 1 Comm: repro Not tainted 7.2.0-07732-g9328b3b03bdc-dirty #3 PREEMPT(lazy) [ 22.212576] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 22.213750] Call Trace: [ 22.215271] <TASK> [ 22.216242] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.217774] dump_stack_lvl+0x4e/0x70 [ 22.220531] print_report+0x157/0x4b4 [ 22.223202] ? fixup_red_left+0x9/0x30 [ 22.224407] ? complete_report_info+0x83/0x110 [ 22.226679] ? function_graph_enter_regs+0xa76/0xb90 [ 22.228084] kasan_report+0xce/0x100 [ 22.230109] ? function_graph_enter_regs+0xa76/0xb90 [ 22.232860] ? stack_trace_save+0x4/0xd0 [ 22.234156] function_graph_enter_regs+0xa76/0xb90 [ 22.236090] ? kasan_save_stack+0x30/0x50 [ 22.237752] ? __pfx_function_graph_enter_regs+0x10/0x10 [ 22.238694] ? ring_buffer_lock_reserve+0x345/0xf80 [ 22.239628] ? stack_trace_save+0x4/0xd0 [ 22.242121] ? stack_trace_save+0x4/0xd0 [ 22.243588] ftrace_graph_func+0xda/0x160 [ 22.245362] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.246520] 0xffffffffa0000095 [ 22.250528] ? stack_trace_save+0x9/0xd0 [ 22.251757] ? ring_buffer_unlock_commit+0x11d/0x5c0 [ 22.253152] stack_trace_save+0x9/0xd0 [ 22.254264] kasan_save_stack+0x30/0x50 [ 22.273631] kasan_save_track+0x14/0x30 [ 22.276763] kasan_save_free_info+0x3b/0x70 [ 22.278296] __kasan_slab_free+0x43/0x70 [ 22.280157] kmem_cache_free+0xbf/0x3b0 [ 22.282963] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.284001] free_task+0xa2/0x160 [ 22.285699] ? ftrace_stub_direct_tramp+0x10/0x10 [ 22.286752] copy_process+0x2aae/0x7bc0 Initialize the child function graph state immediately after dup_task_struct(), before the first fallible operation.

The advisory is shared at git.kernel.org. The identification of this vulnerability is CVE-2026-97937 since 09/25/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details are known, but no exploit is available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 09/25/2026).

Upgrading to version 7.2.7 or 7.3-rc3 eliminates this vulnerability. Applying the patch 1fadebbbf31f65beba353fa9d1373bf183e03fed/08cacffeef8f64f1a222c93467ca84f24a46c953 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.3-rc1
• 7.3-rc2

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Discussion