CVE-2021-46904

What it is

In the Linux kernel, the following vulnerability has been resolved: net: hso: fix null-ptr-deref during tty device unregistration Multiple ttys try to claim the same the minor number causing a double unregistration of the same device. The first unregistration succeeds but the next one results in a null-ptr-deref. The get_free_serial_index() function returns an available minor number but doesn't assign it immediately. The assignment is done by the caller later. But before this assignment, calls to get_free_serial_index() would return the same minor number. Fix this by modifying get_free_serial_index to assign the minor number immediately after one is found to be and rename it to obtain_minor() to better reflect what it does. Similary, rename set_serial_by_index() to release_minor() and modify it to free up the minor number of the given hso_serial. Every obtain_minor() should have corresponding release_minor() call.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of service disruption.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2024-02-26 16:27 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:15 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.3% in the next 30 days (EPSS).
• Severity: 5.5 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2024-02-26 16:27 UTC

Last modified

2026-06-17 04:15 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-476 · NULL pointer dereference

Record status

Modified

Affected

• Linux Kernel < 4.4.268
• Linux Kernel < 4.9.268
• Linux Kernel < 4.14.232
• Linux Kernel < 4.19.187
• Linux Kernel < 5.4.112
• Linux Kernel < 5.10.30
• Linux Kernel < 5.11.14

Attack profile CVSS 3.1 · 5.5

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-46904.md and follow it. Check whether this project is affected by CVE-2021-46904. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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