---
id: "CVE-2026-99219"
kind: "vulnerability"
aliases: ["CVE-2026-99219"]
title: "Linux kernel: ftrace uninitialized variable crashes reading available_filter_functions"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["ftrace", "linux-kernel", "runtime"]
not_affected_if: ["no-ftrace-access"]
published_at: "2026-11-02T16:17:45+00:00"
first_seen_at: "2026-11-02T16:24:05+00:00"
updated_at: "2026-11-02T16:27:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99219", "first_seen_at": "2026-11-02T16:24:05+00:00"}]
---

# Linux kernel: ftrace uninitialized variable crashes reading available_filter_functions

In the Linux kernel's ftrace tracing code, a module name variable is left uninitialized when a symbol lookup fails during module load or unload. Reading the available_filter_functions file in that window can dereference the garbage value and cause a general protection fault.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-11-02T16:24:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99219

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

ftrace: Initialize modname and offset in print_rec()

print_rec() leaves 'modname' and 'offset' uninitialized and
kallsyms_lookup() only sets them on success. When the lookup fails like
when a module is being loaded or unloaded, 'modname' holds a garbage
value, passes the 'if (modname)' check, and is dereferenced by
seq_printf().

  Oops: general protection fault
  RIP: 0010:string+0x48/0xe0
  Call Trace:
   vsnprintf+0x1f5/0x650
   seq_printf+0x8e/0xb0
   print_rec+0x6c/0xc0
   t_show+0x4c/0x440
   seq_read_iter+0x119/0x480

This can be triggered by reading available_filter_functions while a
module is being loaded or unloaded.

Initialize both variables so a failed lookup skips the module name.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_