Skip to main content
VulnerabilityPublished Updated

CVE-2026-64235: Linux kernel · x86/ftrace: Relocate %rip-relative percpu refs in dynamic trampolines

Affects Linux kernelSource CVE Database V5

0

Not known to be exploited · CVSS 8.1 High · fixed in d59cc66b702757e3c5a711e78a38583eac0c2738 : patch Linux kernel soon.

Data as of 26 Oct 2026, 17:30 UTC

CVSS 3.1 base score
8.1High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 25% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Total control over the software or total information disclosure

CISA SSVC assessment, 2026-10-16.

Patch
Available – fixed in d59cc66b702757e3c5a711e78a38583eac0c2738, a17dc12bfed8868e6a86f3b45c16065a70641acb, 8093442a2d1d4b42b9340a86023ccb2afb30b93a +1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade Linux kernel to d59cc66b702757e3c5a711e78a38583eac0c2738, a17dc12bfed8868e6a86f3b45c16065a70641acb, 8093442a2d1d4b42b9340a86023ccb2afb30b93a or 9edff632ca216169846f8a63a5a3dc467e239c7a.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ 59bec00ace28d565ae0a68b23063ef3b961d82d5, < d59cc66b702757e3c5a711e78a38583eac0c2738
Fixed in
  • d59cc66b702757e3c5a711e78a38583eac0c2738
LinuxLinuxAffected
  • ≥ 59bec00ace28d565ae0a68b23063ef3b961d82d5, < a17dc12bfed8868e6a86f3b45c16065a70641acb
Fixed in
  • a17dc12bfed8868e6a86f3b45c16065a70641acb
LinuxLinuxAffected
  • ≥ 59bec00ace28d565ae0a68b23063ef3b961d82d5, < 8093442a2d1d4b42b9340a86023ccb2afb30b93a
Fixed in
  • 8093442a2d1d4b42b9340a86023ccb2afb30b93a
LinuxLinuxAffected
  • ≥ 59bec00ace28d565ae0a68b23063ef3b961d82d5, < 9edff632ca216169846f8a63a5a3dc467e239c7a
Fixed in
  • 9edff632ca216169846f8a63a5a3dc467e239c7a
LinuxLinuxAffected
  • =6.9
Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: x86/ftrace: Relocate %rip-relative percpu refs in dynamic trampolines With CONFIG_CALL_DEPTH_TRACKING enabled on an x86 retbleed-affected platform (eg: Skylake), with retbleed=stuff, registering a dynamic ftrace trampoline crashes on the first call into the traced function: BUG: unable to handle page fault for address: ffff88817ae18880 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 4b53067 P4D 4b53067 PUD 0 Oops: Oops: 0002 [#1] SMP PTI CPU: 3 UID: 0 PID: 187 Comm: usleep Not tainted 7.0.10 #243 PREEMPT(full) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014 Code: 24 78 00 00 00 00 48 89 ea 48 89 54 24 20 48 8b b4 24 b8 00 00 00 48 8b bc 24 b0 00 00 00 48 89 bc 24 80 00 00 00 48 83 ef 05 <65> 48 c1 3d 1f a8 b6 02 05 48 8b 15 f6 00 00 00 4c 89 3c 24 4c 89 Call Trace: <TASK> ? find_held_lock ? exc_page_fault ? lock_release ? __x64_sys_clock_nanosleep ? lockdep_hardirqs_on_prepare ? trace_hardirqs_on __x64_sys_clock_nanosleep do_syscall_64 ? exc_page_fault ? call_depth_return_thunk entry_SYSCALL_64_after_hwframe ... Kernel panic - not syncing: Fatal exception This small reproducer allows to easily trigger the crash: # echo 'p __x64_sys_clock_nanosleep' > /sys/kernel/tracing/kprobe_events # echo 1 > /sys/kernel/tracing/events/kprobes/p___x64_sys_clock_nanosleep_0/enable # usleep 1 Monitoring the crash under GDB points to the exact instruction in charge of incrementing the call depth: sarq $5, %gs:__x86_call_depth(%rip) This instruction matches the one inserted by the ftrace_regs_caller from ftrace_64.S. This emitted code was likely working fine until the introduction of 59bec00ace28 ("x86/percpu: Introduce %rip-relative addressing to PER_CPU_VAR()"): it has made the call depth accounting addressing relative to $rip, instead of being based on an absolute address. As this code exact location depends on where the trampoline lives in memory, the corresponding displacement needs to be adjusted at runtime to actually correctly find the per-cpu __x86_call_depth value, otherwise the targeted address is wrong, leading to the page fault seen above. Fix the %rip-relative displacement of the copied CALL_DEPTH_ACCOUNT instruction (from ftrace_regs_caller) by calling text_poke_apply_relocation(), as it is done for example by the x86 BPF JIT compiler through x86_call_depth_emit_accounting(). This corrects both CALL_DEPTH_ACCOUNT slots, in ftrace_caller and ftrace_regs_caller. [ bp: Massage. ]

References

Community reviews

Loading reviews…