Researchers Discover AirDrop Security Flaw That Could Expose Personal Data to Strangers

AirDrop is a feature that allows Apple devices to securely and conveniently transfer files, photos, and more between each other wirelessly. Users can share items with their own devices, friends, family, or even strangers. The convenience and ease of use, however, may be undermined by a newly discovered security flaw.

airdrop logo
Researchers at TU Darmstadt have discovered that the process which AirDrop uses to find and verify someone is a contact on a receiver's phone can expose private information. AirDrop includes three modes; Receiving Off, Contacts Only, Everyone. The default setting is Contacts Only, which means only people within your address book can AirDrop photos, files, and more to your device.

The researchers discovered that the mutual authentication mechanism that confirms both the receiver and sender are on each other's address book could be used to expose private information. The researchers claim that a stranger can use the mechanism and its process within the range of an iOS or macOS device with the share panel open to obtain private information. As the researchers explain:

As an attacker, it is possible to learn the phone numbers and email addresses of AirDrop users – even as a complete stranger. All they require is a Wi-Fi-capable device and physical proximity to a target that initiates the discovery process by opening the sharing pane on an iOS or macOS device.

The discovered problems are rooted in Apple's use of hash functions for "obfuscating" the exchanged phone numbers and email addresses during the discovery process. However, researchers from TU Darmstadt already showed that hashing fails to provide privacy-preserving contact discovery as so-called hash values can be quickly reversed using simple techniques such as brute-force attacks.

To determine whether the other party is a contact, AirDrop uses a mutual authentication mechanism that compares a user's phone number and email address with entries in the other user's address book.

According to the researchers, Apple was informed of the flaw in May of 2019, and despite several software updates since then, the flaw remains.

Tag: AirDrop

Popular Stories

iOS 26

iOS 26.1 Coming Soon: New Features for Your iPhone and Release Date

Monday October 27, 2025 7:55 am PDT by
The upcoming iOS 26.1 update includes a handful of new features and changes for iPhones, including a toggle for changing the appearance of the Liquid Glass design, "slide to stop" for alarms in the Clock app, and more. Below, we outline key details about iOS 26.1. Release Date Given that Apple has yet to seed an iOS 26.1 Release Candidate, which is typically the final beta version, the...
maxresdefault

Apple TV 4K Could Still Launch Before 2025 Ends: All the Rumored Features

Monday October 27, 2025 4:51 pm PDT by
Apple is designing an updated version of the Apple TV 4K, and rumors suggest that it could come out sometime in the next couple of months. We're not expecting a major overhaul with design changes, but even a simple chip upgrade will bring major improvements to Apple's set-top box. Subscribe to the MacRumors YouTube channel for more videos. We've rounded up all the latest Apple TV rumors. ...
iOS 26

6 New Things Your iPhone Can Do in iOS 26.1

Wednesday October 29, 2025 4:22 am PDT by
Apple is about to drop iOS 26.1, the first major point release since iOS 26 was rolled out in September, and there are at least six notable changes and improvements to look forward to. We've rounded them up below. Apple has already provided developers and public beta testers with the release candidate version of iOS 26.1, which means Apple will likely roll out the update to all compatible...
M6 MacBook Pro Feature 1

M6 MacBook Pro: Release Date, Pricing, and What to Expect

Monday October 27, 2025 9:15 am PDT by
Apple this month refreshed the 14-inch MacBook Pro base model with its new M5 chip, and higher-end 14-inch and 16-inch MacBook Pro models with M5 Pro and M5 Max chips are expected to follow in early 2026. However, these machines will represent the final update to the current design, with Apple reportedly developing a completely new version of the MacBook Pro packed with next-generation hardware...
iOS 26

Apple Seeds iOS 26.1, iPadOS 26.1, and macOS Tahoe 26.1 Release Candidates

Tuesday October 28, 2025 1:07 pm PDT by
Apple today provided developers and public beta testers with the release candidate versions of upcoming iOS 26.1, iPadOS 26.1, macOS Tahoe 26.1, tvOS 26.1, watchOS 26.1, and visionOS 26.1 updates for testing purposes. The RCs betas come a week after Apple released the fourth betas. The new betas can be downloaded from the Settings app on a compatible device by going to General > Software...
iOS 26 Battery Glass Feature

iOS 26.1 Beta Liquid Glass Battery Drain Test: Tinted vs Clear Mode

Friday October 24, 2025 2:30 pm PDT by
In the fourth iOS 26.1 beta, Apple added a "Tinted" option that reduces the translucency of Liquid Glass for those who prefer a more opaque look. I saw some comments wondering whether the setting might preserve battery life, so I thought I'd do some testing. Test Settings I did four separate tests using the iPhone 17 Pro Max, and I kept the parameters as similar as possible. Here are the...
ios 26 digital id passport wallet

Apple Says U.S. Passport Feature on iPhone is Coming Soon

Monday October 27, 2025 7:41 am PDT by
You will "soon" be able to add a digital version of your U.S. passport to your iPhone, according to Jennifer Bailey, vice president of Apple Pay and Apple Wallet. Bailey reiterated that the feature is coming soon during her keynote at the Money20/20 USA conference in Las Vegas on Sunday. On its iOS 26 page, Apple says the delayed feature will be "coming later this year." Apple's...
All Screen iPhone 2027 Feature 1

iPhone XX? 6 Features Rumored for Apple's 20th Anniversary iPhone

Monday October 27, 2025 4:01 pm PDT by
For the 10th anniversary iPhone that came out in 2017, Apple introduced the iPhone X with Face ID, notch, and minimized bezels, providing more display space than ever before. The 20th iPhone anniversary is approaching and Apple wants to take the iPhone X design even further. We're two years away from the 2027 iPhone, but it's tough for Apple to keep major changes under wraps. We've rounded...
macos tahoe

Here Are Apple's Release Notes for macOS Tahoe 26.1

Tuesday October 28, 2025 1:21 pm PDT by
Apple today provided developers and public beta testers with the release candidate version of macOS Tahoe 26.1, which means the update will likely see a public launch next week. The release candidate includes notes on what's in the update, so we have a full picture of the new features that Apple has included. macOS Tahoe 26.1 adds AutoMix support over AirPlay, improved FaceTime audio...

Top Rated Comments

Apple_Robert Avatar
59 months ago
This is not good. If Apple was in fact informed specifically about this vulnerability in 2019, I take umbrage with Apple not having taken the proper steps to secure AirDrop.
Score: 12 Votes (Like | Disagree)
dannyyankou Avatar
59 months ago

According to the researchers, Apple was informed of the flaw in May of 2019, and despite several software updates since then, the flaw remains. We've reached out to Apple for comment and will update this article if we hear back.
I’m sure now that they made this public, Apple will move with more urgency. Apple is usually better fixing security flaws, I’m disappointed.
Score: 9 Votes (Like | Disagree)
Unregistered 4U Avatar
59 months ago

And that is the SIMPLE process. Why is this even news?
Because there’s really very little “security” news that’s even worth reporting, but the researchers still need attention and validation. But, their reports are of the sort that remind me my home has a security hole in that my chimney provides access to my house once you tear down the external facing wall. However, very few people are concerned by or will do anything about this vulnerability. My garage door? COMPLETELY vulnerable to a brute force attack by a tank. Why won’t garage door manufacturers DO anything about this?
Score: 8 Votes (Like | Disagree)
Unregistered 4U Avatar
59 months ago

Yeah that doesn’t sound great. I wonder how many bad actors there actually are out there taking advantage of this loophole though?

Even though this obviously needs to be patched, does anyone seriously believe that any "bad actor" is going to go through this much work so he can sit in a Starbucks and steal someone's phone number? :)
No :) Folks need to remember that their life REALLY isn’t actually all that interesting, anyone interested IN their information is not going to waste time on an AirDrop brute force hack. If they are THAT close and REAAAAAALLLLY want your information, they can readily get access to it using one of the devices below.


Attachment Image
Score: 8 Votes (Like | Disagree)
13astion Avatar
59 months ago

This is not good. If Apple was in fact informed specifically about this vulnerability in 2019, I take umbrage with Apple not having taken the proper steps to secure Handoff.
It’s AirDrop, not Handoff. The latter is used by ONE user to transfer control or data between multiple devices that are already in their control (and logged into).

AirDrop allows TWO different users logged into TWO devices under their own control to share data. Hence the need for authentication.

And the attack vector is super specific... a black hat *physically nearby* has to try to grab your data while you initiate the AirDrops (and I would guess most AirDrops are small things: a contact card, a photo, a doc... all which take seconds to transfer), and THEN brute force the hashes... for what? A bit of stolen PII?

Yes, it’s *possible* for someone to do this... but *probable*? Naahh. Which is why Apple hasn’t prioritized it. In risk management you have to prioritize the risks by probability and impact... this one is pretty low on both counts.
Score: 7 Votes (Like | Disagree)
ikramerica Avatar
59 months ago

Namely, their email address and telephone number. Not their bank account data, not their social security number. Notice how they obfuscate “PRIVATE DATA OOOH SCARY” from what’s actually shared.

There is a VERY VERY good chance that your “private data” in this case is already on a list some ne’er do well purchased last month… and they didn’t even have to be within AirDrop range to get it! Next they’ll be reporting that
“Folks can gain access to your email address by ASKING you for it. If you fall for the exploit and provide them with your email address THEY WILL HAVE IT!! We reached out to Apple asking if they plan to stop providing email addresses so that people aren’t able to leak them and they looked at us funny and shooed us away.”
I am pretty sure you can get all that juicy data by putting a name in a google search. Plus home address, previous addresses, criminal record, etc.

I do think the odds of someone brute forcing an airdrop in close
proximity to you in order to discover your phone number and email is pretty remote. One assumes that if they are going to all that effort to target you, they already know your name.

One question for the researchers: does this mean turning on “everyone” is more secure as no matching is attempted?
Score: 7 Votes (Like | Disagree)