A single toxic employee can ruin an entire company's culture.

Toxic workers can make the office uncomfortable and uninviting, hinder productivity and morale, and even cause others to quit their jobs, according to the Society of Human Resource Management. They might be disruptive, inauthentic or just plain hard to get along with.

The behavior may seem clear to other people, but it's often difficult to know whether you're negatively affecting the people around you, and asking them directly can be awkward.

So, whether you want help recognizing the toxic employees around you — or you'd like to avoid becoming one yourself — watch out for these three red flags, CEOs say.

The entitled employee

Don't ever act like you're owed a promotion or raise, says Tom Gimbel, CEO of staffing and recruiting firm LaSalle Network.

"[People who say] 'I'm only going to do what's in my job description, I'm not going the extra mile, I'm not going to commit time to this' and expect to be rewarded" aren't desirable employees, Gimbel tells CNBC Make It.

It makes you look like you think you're "above" your peers, he adds.

Sometimes, employees are caught off-guard when colleagues with less tenure get promoted first, but time alone doesn't entitle anyone to a promotion. It can help, of course — but promotions often hinge more on the quality of your work, the strength of your workplace relationships and your track record of moving the company forward, notes Gimbel.

If you see that your colleagues "do more" than you, find a passion project or creative ways to contribute on the job to help you stay competitive, he advises.

The gaslighter

Everyone makes mistakes sometimes. Passing the blame is a major red flag, says Talia Fox, CEO of executive consulting firm KUSI Global.

"Owning your mistakes and having a high level of integrity is so critical," Fox says. "Just show up and have some honesty around it."

Once, Fox says, she gave an employee an assignment and made sure to overcommunicate her expectations ahead of time. When the employee turned in the work, it contained a noticeable error — and they blamed Fox, saying her instructions were unclear.

"We had to have a conversation about the impact that [being gaslit] was having on me," says Fox, noting that the person later owned up to their behavior.

Gaslighting is both manipulative and mean, says Fox. Instead of deflecting your mistakes, apologize and do the work to make it right.

The yes man

You may want to respond "yes" to everything your boss says, even when you don't agree with them. That's a red flag, according to billionaire serial entrepreneur Mark Cuban.

When seeking new partners or employees, Cuban looks for the complete opposite, favoring those who "complement" his skill set but are unafraid to speak up when they disagree with him, he said during a MasterClass course released in February.

Stifling your own suggestions and opinions can make you seem inauthentic and untrustworthy. If your boss is anything like Cuban, they'll respect you more for being vocal about your ideas — using evidence and research to back them up, when necessary.

"I don't need people to tell me yes," Cuban said. "I can tell myself yes ... I need people who are going to challenge conventional wisdom and challenge me, and when they think I've done something wrong, say, 'I think you think you're making a mistake here, and this is why.'"

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