CVE-2021-45256

Publication date 22 December 2021

Last updated 5 May 2026

Ubuntu priority

Why this priority?

Cvss 3 Severity Score

Score breakdown

Description

A Null Pointer Dereference vulnerability existfs in nasm 2.16rc0 via asm/preproc.c.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
nasm	26.04 LTS resolute	Vulnerable, fix deferred
	25.10 questing	Vulnerable, fix deferred
	25.04 plucky	Ignored end of life, was deferred (2025-05-05)
	24.10 oracular	Ignored end of life, was needs-triage
	24.04 LTS noble	Vulnerable, fix deferred
	23.10 mantic	Ignored end of life, was needs-triage
	23.04 lunar	Ignored end of life, was needs-triage
	22.10 kinetic	Ignored end of life, was needs-triage
	22.04 LTS jammy	Vulnerable, fix deferred
	21.10 impish	Ignored end of life
	21.04 hirsute	Ignored end of life
	20.04 LTS focal	Vulnerable, fix deferred
	18.04 LTS bionic	Vulnerable, fix deferred
	16.04 LTS xenial	Vulnerable, fix deferred
	14.04 LTS trusty	Ignored end of standard support

Notes

juliaphoebe

no patch is available, and the only poc does not actually produce the issue it says it does. There is however code in asm/preproc.c that is theoretically vulnerable to a null pointer deref.

nickgalanis

As per Debian this is a crash in CLI tool, with no security impact. No upstream patch available as of 2026-05-05

Severity score breakdown

Parameter	Value
Base score	5.5 · Medium
Attack vector	Local
Attack complexity	Low
Privileges required	None
User interaction	Required
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	High
Vector	CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H