This critical Linux vulnerability is putting millions of systems at risk – how to protect yours


This critical Linux vulnerability is putting millions of systems at risk - how to protect yours

Kerry Wan/ZDNET

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ZDNET key takeaways

  • Copy Fail is a dangerous Linux vulnerability.
  • This flaw makes gaining root access easy for attackers.
  • Copy Fail affects millions of Linux systems.

CVE-2026-31431, also known as Copy Fail, is a critical Linux kernel vulnerability that’s been hiding out since 2017 and is now getting the security spotlight it deserves.

Also: This simple Linux tweak fixes crashes automatically – and it costs me nothing

Oftentimes, Linux vulnerabilities can be a bit overblown, but not in this case. Copy Fail is serious business and should be considered an issue that must be mitigated.

What is Copy Fail?

Let’s talk about Copy Fail in terms that anyone can understand.

Imagine your computer’s memory as a chalkboard, where a teacher keeps track of your grades in real time. You don’t allow students to use either chalk or erasers, so they can’t change their grades. The “Copy Fail” vulnerability is like a sneaky student who somehow gains access to an eraser and chalk, and he changes just his grade while you’re not looking.

Essentially, Copy Fail is a flaw in the Linux system that is in charge of handling security for certain types of data. The flaw allows an attacker, who has just basic access to a system, to alter a crucial piece of data that exists within the computer’s RAM. Once the change is made, the altered data can trick the system into thinking that the attacker is the root user, giving the attacker full control over the system.

Also: 6 reasons a minimal Linux install might be the smartest move you make

Think of it this way: A janitor takes the nameplate from the boss’s office and slaps it on the wall beside his closet so everyone thinks he is the boss.

That’s Copy Fail.

A difference between Copy Fail and other vulnerabilities that have hit Linux is that this one doesn’t require specific timing or certain events to happen in an exact order. It’s much easier, and its effects can be devastating.

A bit more detail

For those who want a bit more detail about Copy Fail: It abuses the AF_ALG socket interface and splice() system call to overwrite a mere 4 bytes in the kernel’s page cache for any readable file. Once this occurs, attackers can then modify the setuid binaries, such as the su command, that are in memory to gain root access.

Copy Fail is different from “race condition” exploits because it’s a stable, straight-line vulnerability that doesn’t require timing-dependent retries to elevate permissions.

Also: The first 8 Linux commands every new user should learn

Copy Fail affects all Linux kernels from 4.14 to 6.19.12. You read that right: kernels from 2017 to the present.

According to the Xint Code Research Team, “This finding was AI-assisted, but began with an insight from Theori researcher Taeyang Lee, who was studying how the Linux crypto subsystem interacts with page-cache-backed data. He used Xint Code to scale his research across the entire crypto subsystem, and Copy Fail was the most critical finding in the report.”

How to avoid Copy Fail

The easiest way to mitigate the Copy Fail Linux vulnerability is to update your kernel to the latest version. To find out if your kernel has been patched against Copy Fail, issue the following command:

dpkg -l kmod grep -qE ‘^algif_aead ‘ /proc/modules && echo “Affected module is loaded” || echo “Affected module is NOT loaded”

If your kernel has been patched, you’ll see “Affected module is NOT loaded.” If your kernel has not been patched, you’ll see “Affected module is loaded.” If you run into the latter, make sure to update your system and rerun the command. If, after an update, your system is still not patched, you can disable the algif_aead module with the command:

install algif_aead /bin/false” > /etc/modprobe.d/disable-algif.conf

Also: You can use Linux 7.0 on these 7 distros today – here’s what to expect

You can then unload the module with:

rmmod algif_aead

You now know enough about Copy Fail to stay protected.





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If Game Two of their first-round playoff series with the Denver Nuggets saved the 2025-26 season for the Minnesota Timberwolves, Game Three showed why it should be saved. 

The Timberwolves were a different beast while decisively thumping the Nuggets, 113-96 Thursday night at Target Center, in a game that wasn’t nearly that close. These Wolves were the mythical creature we’d heard about in preseason lore, purposefully locked and loaded to be both marauding and staunch. They owned both ends of the court, gleefully transferring back and forth from irresistible force to immovable object. 

A quartet of Timberwolves deserve special mention, but it begins with Jaden McDaniels. After his team had toppled Denver to even the series at a game apiece Monday night, McDaniels used the sizable chip on his shoulder to etch some graffiti into the public discourse, casually castigating the most prominent Nuggets players by name as “bad defenders” in a matter-of-fact manner that had the media compelling him to confirm what he had just said. 

Trash talk is fleetingly fungible in the jaundiced social environment of 2026, functioning more like coupons than currency in that it needs to be rapidly leveraged before its expiration date. The common perception naturally was that McDaniels was calling out the Nuggets. But in a more subtle, profound way, he was also putting his teammates on notice. 

All season long the Timberwolves have procrastinated on their full potential, frequently demonstrating that their preseason talk about maturity and commitment was cheap. By contrast, those words uttered by McDaniels were expensive. He had just picked a fight with the opponent, leaving open the question of how many of his teammates would join him in the fray. 

That he would lead the charge was established early, after the Timberwolves’ top two scorers, Anthony Edwards and Julius Randle, had each missed a pair of open looks against Denver’s bad defenders in the game’s first 90 seconds.  

With the game still scoreless, the NBA’s best pick-and-roll combo, Nikola Jokic and Jamal Murray, were clustered around the foul line with Minnesota’s best defenders, McDaniels and Rudy Gobert. As they jammed up Jokic, McDaniels picked the ball loose and started sprint-dribbling the other way. To no one’s surprise, Donte “Ragu” DiVincenzo was also on his horse in transition, receiving a pass from McDaniels and then lobbing it back for a Jaden slam against a hapless Murray and Murray’s late-arriving teammate, Cam Johnson, who committed the foul that allowed McDaniels to finish with the “and-1” free throw. 

On the Timberwolves next offensive possession, McDaniels muscled his way to two offensive rebounds, feeding Ragu off the first one for a missed three-pointer, which he corralled for the second one and executed the putback in traffic. It was McDaniels 5, Nuggets 0, setting the tone for a game in which not only did the Wolves never trail, but never let the lead go under double digits after McDaniels made a consecutive pair of driving layups eight minutes into the game. 

“Spectacular. I thought his activity offensively in the first quarter was outstanding,” said Wolves coach Chris Finch after the game. “He was inspirational.” 

Among the most inspired were McDaniels fellow wing players, Ragu and Ayo Dosunmu. Ragu is exactly the kind of player who will have your back in a squabble, and his galvanized performance seemed borne of satisfaction that someone else had clarified the mission. As usual, the Timberwolves were at their best with him on the court: +20 in the 32:54 he played, -3 in the 15:06 he sat. 

“He makes so many hustle plays, momentum plays, different styles of plays.” Finch raved. “He’ll make a shot, get a transition bucket, he’ll rebound, get a steal, blow something up. So many different plays. He’s just a basketball player.”

Related: How the Timberwolves sparked a season-saving Game 2 comeback over the Nuggets in Denver

Then there was Ayo, whose fearless, blazing, bee-lines for the bucket were quicksilver kryptonite for a Nuggets defense that is neither swift nor rugged. “I’ve been waiting for him to wake up a little bit in this series,” Finch accurately observed. “The downhill mindset that he played with all season for us was back.”

Back with the sort of multipurpose propulsion that leaves witnesses with giddy whiplash. Ayo led the team with 25 points and 9 assists in 32 minutes of time-lapse hoops, the lone blemish being three clanks from long range. Why chuck treys when you can so easily undress players in the paint? Ayo was 10-for-12 on two-pointers and none of those dozen shots came from anywhere but beneath the rim. Five of his nine dimes likewise yielded layups or dunks, which means he personally accounted for 30 of the 68 points in the paint by the Timberwolves on Thursday, doubling up the Nuggets’ 34.

Which brings us to the non-wing in Game 3’s ring of honor, Rudy Gobert. For the third straight game, Gobert blunted the supposed advantage Denver had with the magical playmaker Nikola Jokic at the controls. Suffice to say that in the last five quarters, Jokic has shot 8-for-33 from the floor. If that continues, the Nuggets are toast in this series. 

When I asked Finch after the game if the herculean job Gobert was doing on Jokic made planning his defense simpler and better thus far, he replied, “Rudy is making all of us look good right now with his defense.” 

Amen.

If there is an asterisk on this game, it would be the absence of Denver’s brutishly versatile power forward Aaron Gordon. Nuggets coach David Adelman should be given a lot of credit for his honesty and transparency in dealing with the media during his first full season at the helm, but it came back to bite him and his team during the pregame presser, when he was clearly rattled and dejected by the sudden unavailability of Gordon, whose playing status went to “probable” to “out” in a period of a few hours due to a chronic calf strain. 

Gordon is far and away his team’s best defender, making the timing of his injury especially troublesome in the wake of McDaniels laying down his marker. Rattled is a good way to describe the entire team’s performance in the first quarter, an emotional wounding that needs to heal as fast as Gordon’s body if the Nuggets are going to be competitive in a series that had dramatically been flipped on its head over the past three days. 

That the Timberwolves played with such dominance despite mediocre outings from Ant and Randle would be a good thing for both of those current cornerstones to keep in mind. Ant was beset by foul trouble and Randle had a solid second quarter, but it stood out that neither player fully embraced what so often works on offense when the Wolves are at their best: Push the pace, move the ball, move without the ball, and make quick decisions. Ant and Randle can still be first among equals and blend into that catechism if they stay attuned to the possibilities of a greater good, one that all of sudden doesn’t have to end with them being postseason fodder for the Spurs or the Thunder. 

Not when you’ve got three wings at a collective peak, with a chaser of Rudy semi-clowning the Joker. 



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