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Response snapshot Nov 8, 2026, 22:35 UTC

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VulnerabilityCVE-2026-64235

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

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:…

At a glance

Exploited
Not known
Severity
8.1 High (CVSS 3.1)
Chance of exploitation
0.3% in the next 30 days
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-64235 (opens a new tab)

What happened

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.

Continue reading

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:

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. ]

Scores and how they were measured

CVSS base severity

8.1

Version 3.1As of

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.3%

Scored Percentile 26.0%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    NVD CVE-2026-64235 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  5. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-64235, scored 2026-11-08. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 8). Linux kernel: x86/ftrace: Relocate %rip-relative percpu refs in dynamic trampolines (CVE-2026-64235). https://kevwire.com/record/CVE-2026-64235

MLA

"Linux kernel: x86/ftrace: Relocate %rip-relative percpu refs in dynamic trampolines (CVE-2026-64235)." KEVWire, 8 Nov. 2026, kevwire.com/record/CVE-2026-64235.

Chicago

KEVWire. "Linux kernel: x86/ftrace: Relocate %rip-relative percpu refs in dynamic trampolines (CVE-2026-64235)." Last modified November 8, 2026. https://kevwire.com/record/CVE-2026-64235.

Evidence summary (plain text)

Linux kernel: x86/ftrace: Relocate %rip-relative percpu refs in dynamic trampolines (Jul 24, 2026).
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:…
CVSS 8.1 (version 3.1; evidence as of Nov 8, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-64235).
EPSS 0.3% for the following 30 days, scored Nov 8, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-64235&date=2026-11-08).
Sources:
NVD CVE-2026-64235: https://nvd.nist.gov/vuln/detail/CVE-2026-64235
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-08T15:56:13.358Z&lastModEndDate=2026-11-08T17:25:56.467Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-08T15:20:57.540Z&lastModEndDate=2026-11-08T16:55:56.207Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-11-08T14:46:00.078Z&lastModEndDate=2026-11-08T16:20:55.703Z&resultsPerPage=500&startIndex=0
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-64235&date=2026-11-08
Record ID: CVE-2026-64235.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 8, 2026, 20:31 UTC. Ingestion is not an independent editorial investigation.

NVD status: Modified. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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