Intel has confirmed that new problems discovered with its processor chips mean that some computer owners face a performance slowdown.
The company has said that data centres are likely to be worst affected by the fixes required.
But it added that the impact on most PC owners should be minimal.
The so-called Zombieload vulnerability follows the disclosure of the earlier Spectre, Meltdown and Foreshadow bugs last year.
The latest flaw could theoretically allow an attacker to spy on tasks being handled by any Intel Core or Xeon-branded central processing unit (CPU) released since 2011.
Amazon Web Services, Microsoft Azure and Google Cloud are among the major cloud computing platforms to power their data centres with the technology.
Zombieload was discovered by researchers at Graz University of Technology in Austria and KU Leuven university in Belgium.
They said it could allow hackers to steal sensitive data or provide the means to unscramble encrypted files.
"[This could affect] user-level secrets, such as browser history, website content, user keys, and passwords, or system-level secrets, such as disk encryption keys," they explained.
They added that it was currently unclear whether any such attack would leave a trace, or if anyone had actually exploited the flaw to date.
Intel has said that it believes that carrying out such an attack would be "a very complex undertaking" but is recommending that users download security updates from Microsoft, Apple and Linux-based operating system providers that will address the issue.
The chip-maker has indicated that the biggest performance hit is likely to involve data centre servers handling tasks that use the programming language Java.
One graph shows such activity running at 81% of the speed it used to, once a software patch has been applied.
But Apple has warned that its own tests have shown as much as a 40% reduction in performance when Macs handle certain computing-intensive workloads.
Claims that earlier patches to address Spectre and Meltdown would make people's computers feel sluggish proved to be largely overstated, although some users have reported problems.
These new side channel vulnerabilities (zombieload, fallout, etc) are great finds - the result of hard & creative work by researchers who deserve applause - and they definitely need to be patched.— Matt Linton 🐦👨💻⚕️⚒️🥋🎻 (@0xMatt) May 14, 2019
That said, "terrifying" is something they are not. Keep some perspective, folks.
Before Spectre and Meltdown fixes, I was able to record in 1080p 60fps (but didn’t often record at that frame rate anyway). After the fixes, I could not record anything similar without lag in 1080p 60fps.— Sonicrush007 🌐 (@Sonicrush007) May 14, 2019
Intel's shares closed nearly 1% above their opening price on Monday despite the problem being reported within trading hours.