Root Access Sudo Bug Found to Affect macOS Big Sur

A sudo bug that can grant an attacker root access has been discovered to affect macOS Big Sur (via ZDNet).

sudo bug macos

The security vulnerability, identified last week as "CVE-2021-3156" by the Qualys Security Team, affects sudo, which is a program that allows users to run commands with the security privileges of another user, such as an administrator. The bug triggers a "heap overflow" in sudo that changes the current user's privileges to enable root-level access. This can give an attacker access to the entire system. An attacker would need to gain low-level access to a system first to be able to exploit the bug, such as via planted malware.

Sudo is part of many Unix-like systems, including macOS, but it was initially unknown if the vulnerability affected Mac machines since it was only tested by Qualys on Ubuntu, Debian, and Fedora. Security researcher Matthew Hickey has now confirmed that the most recent version of macOS, macOS Big Sur 11.2 can be subject to the sudo attack.

Last week, there was speculation that the macOS Big Sur 11.2 update may address the sudo vulnerability, though it was not definitively known at the time if the bug would affect macOS. While it was found that sudo was left unchanged in macOS Big Sur 11.2, it is now clear that macOS is affected by the exploit.

With some minor modifications, Hickey found that the sudo bug could be used to grant attackers access to macOS root accounts, and the discovery has now been verified by Carnegie Mellon University vulnerability analyst Will Dormann.

Apple has reportedly been notified of the CVE-2021-3156 vulnerability, and due to the severity of the issue, a patch will likely be released soon.

Popular Stories

mac mini thermal architecture feature

New Mac Mini Has Modular Storage, 256GB Model Will Have Faster SSD

Friday November 8, 2024 7:06 am PST by
Apple has returned to using two 128GB storage chips in the new Mac mini with 256GB of storage, according to a partial teardown video shared on social media today. This means the base-model Mac mini with the M4 chip will not have significantly slower SSD speeds compared to higher-end configurations of the computer with 512GB, 1TB, or 2TB of storage, as multiple NAND chips allows for faster SSD...
Generic iOS 18

Everything New in iOS 18.2 Beta 2

Monday November 4, 2024 12:34 pm PST by
Apple today seeded the second betas of upcoming iOS 18.2 and iPadOS 18.2 updates to developers, and Apple is continuing to refine the Apple Intelligence capabilities. There are also a handful of smaller features that are worth knowing about. Find My Find My has a new option to Share Item Location with an "airline or trusted person" that can help you locate something that you've misplaced....
iphone passcode green

Cops Suspect iOS 18 iPhones Are Communicating to Force Reboots, Making Unlocking Harder

Thursday November 7, 2024 2:20 pm PST by
Law enforcement officials in Detroit, Michigan are warning other police officers about an alleged iPhone change that causes Apple devices stored for forensic examination to spontaneously restart, reports 404 Media. iPhones that are undergoing examination have apparently been rebooting, which makes them harder to unlock with brute force methods, and Michigan police think that it's due to a...
early apple watch black friday

The Best Early Black Friday Apple Watch Deals

Wednesday November 6, 2024 6:33 am PST by
Black Friday is just around the corner, and Apple Watch deals have begun appearing ahead of the shopping holiday on November 29. In this article, we'll take a look at all of the best early Black Friday Apple Watch deals, including the new Series 10 models. Note: MacRumors is an affiliate partner with some of these vendors. When you click a link and make a purchase, we may receive a small...
iCloud General Feature

Here's What's New in Apple's Updated iCloud Terms and Conditions Taking Effect Next Week

Friday September 13, 2024 7:39 am PDT by
Apple has started notifying users about an upcoming revision to its iCloud Terms and Conditions, which takes effect on Monday, September 16. We compared the text of the upcoming iCloud Terms and Conditions with the current U.S. version from September 18, 2023 and identified four key changes: "Apple ID" references have been changed to "Apple Account" throughout. iCloud users must agree to ...
M4 MacBook Pros Thumb

M4 MacBook Pro Reviews: Processor Benchmarks Impress, New Nano-Texture Option Worth the Extra $150

Thursday November 7, 2024 6:14 am PST by
The first wave of reviews of Apple's new M4-powered MacBook Pro models were published this morning. We've collected some of the latest impressions from YouTube channels and select media outlets below. Apple last month announced the new 14-inch and 16-inch MacBook Pro models, adding next-generation M4, M4 Pro, and M4 Max chips, with Thunderbolt 5 ports on higher-end models, display and camera ...
High Power Mode Feature 2

Apple Expands High Power Mode to MacBook Pro and Mac Mini Models With M4 Pro Chip

Thursday November 7, 2024 12:15 pm PST by
High Power Mode is available on the 14-inch MacBook Pro, 16-inch MacBook Pro, and Mac mini models with the M4 Pro chip, according to Ars Technica's Andrew Cunningham. The feature was previously limited to Macs with Apple's highest-end "Max" chip, so this is the first time it is available on Macs with a "Pro" chip. This is the second time that Apple has expanded availability of High Power...
ipads early bf deals

The Best Early Black Friday iPad Deals

Tuesday November 5, 2024 7:02 am PST by
Black Friday is still a few weeks away, but you can already find great prices on numerous iPads, including the 9th generation iPad, 10th generation iPad, iPad Air, and iPad mini. Note: MacRumors is an affiliate partner with some of these vendors. When you click a link and make a purchase, we may receive a small payment, which helps us keep the site running. Of course, there is a chance that ...

Top Rated Comments

AttoA Avatar
49 months ago

Apple rushing beta software to market, again.
This vulnerability has been present for more than a decade in all sorts of UNIXes! It's not something at all limited to Apple's QA...
Score: 34 Votes (Like | Disagree)
Havalo Avatar
49 months ago


Attachment Image
Score: 31 Votes (Like | Disagree)
mannyvel Avatar
49 months ago

So, mostly free OSes. That's much of a defense....

Devs knew about the potential, and chose not to address it. They would rather rush a beta product to market.
One day you will learn more about software and you will look back at this comment and say "wow, I was totally clueless back then."
Score: 27 Votes (Like | Disagree)
Gabebear Avatar
49 months ago

Wow I thought this would have been patched out in 11.2. Hopefully we will get a
supplemental patch shortly.
It turns most fairly minor security issues into full-blown root exploits… fairly terrifying.
Score: 9 Votes (Like | Disagree)
opfor Avatar
49 months ago

I'd think we'd have better tools/procedures for finding bugs like this a lot sooner.

Is there not an automated tool that can look at some code and say "hey, right here it's possible for a heap overflow to occur and there's no error handling code to deal with it"?
Sure there are tools that catch some of these problems via static analysis etc and there are languages where this class of problems might not even occur.

But it is also true that the day that the CVE was released I updated my Linux servers and got a fixed/patched sudo, while even macOS 11.3 beta1 still has the issue, so this is also indicative of Apple release engineering capabilities, or lack of them.
Score: 8 Votes (Like | Disagree)
justperry Avatar
49 months ago

So is this a zero day, drive-by vulnerability? Or does the attacker have to have physical access?
Nope

"An attacker would need to gain low-level access to a system first to be able to exploit the bug, such as via planted malware."
Score: 8 Votes (Like | Disagree)