What’s Vulnerable › Vulnerabilities

CVE-2025-39683: tracing: Limit access to parser->buffer when trace_get_user failed

• Severity: high (CVSS 7.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-09-05 · updated 2026-10-19
• Weakness: CWE-125

Description

In the Linux kernel, the following vulnerability has been resolved: tracing: Limit access to parser->buffer when trace_get_user failed When the length of the string written to set_ftrace_filter exceeds FTRACE_BUFF_MAX, the following KASAN alarm will be triggered: BUG: KASAN: slab-out-of-bounds in strsep+0x18c/0x1b0 Read of size 1 at addr ffff0000d00bd5ba by task ash/165 CPU: 1 UID: 0 PID: 165 Comm: ash Not tainted 6.16.0-g6bcdbd62bd56-dirty Hardware name: linux,dummy-virt (DT) Call trace: show_stack+0x34/0x50 (C) dump_stack_lvl+0xa0/0x158 print_address_description.constprop.0+0x88/0x398 print_report+0xb0/0x280 kasan_report+0xa4/0xf0 __asan_report_load1_noabort+0x20/0x30 strsep+0x18c/0x1b0 ftrace_process_regex.isra.0+0x100/0x2d8 ftrace_regex_release+0x484/0x618 __fput+0x364/0xa58 ____fput+0x28/0x40 task_work_run+0x154/0x278 do_notify_resume+0x1f0/0x220 el0_svc+0xec/0xf0 el0t_64_sync_handler+0xa0/0xe8 el0t_64_sync+0x1ac/0x1b0 The reason is that trace_get_user will fail when processing a string longer than FTRACE_BUFF_MAX, but not set the end of parser->buffer to 0. Then an OOB access will be triggered in ftrace_regex_release-> ftrace_process_regex->strsep->strpbrk. We can solve this problem by limiting access to parser->buffer when trace_get_user failed.

Affected products

• Debian Linux: 11.0
• Linux kernel: from 4.4.269 before 4.5; from 4.9.269 before 4.10; from 4.14.233 before 4.15; from 4.19.191 before 4.20; from 5.4.118 before 5.5; from 5.10.36 before 5.10.241 — fixed in 4.10, 4.15, 4.20, 4.5, 5.10.241, 5.12

How to fix

Upgrade to a fixed version: Linux kernel 4.10, 4.15, 4.20, 4.5. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/3079517a5ba80901fe828a06998da64b9b8749be
• https://git.kernel.org/stable/c/418b448e1d7470da9d4d4797f71782595ee69c49
• https://git.kernel.org/stable/c/41b838420457802f21918df66764b6fbf829d330
• https://git.kernel.org/stable/c/58ff8064cb4c7eddac4da1a59da039ead586950a
• https://git.kernel.org/stable/c/6a909ea83f226803ea0e718f6e88613df9234d58
• https://git.kernel.org/stable/c/b842ef39c2ad6156c13afdec25ecc6792a9b67b9
• https://git.kernel.org/stable/c/d0c68045b8b0f3737ed7bd6b8c83b7887014adee
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
• https://cert-portal.siemens.com/productcert/html/ssa-032379.html
• https://cert-portal.siemens.com/productcert/html/ssa-082556.html

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