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IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

mysk.blog

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Re: IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

#31

Post by lxgr »

irusensei wrote: post #29

Apple private relay is very flawed but on the other hand most sites that view connections originating from VPN as suspicious seem to be ok with Apple Private Relay. If you have VPN on your router private relay on top of it could be a good way to do ip address laundering.

I find it pretty annoying that iCloud Private Relay does not work together with VPNs.

I mainly use VPNs to access bank sites (or other sites that are annoying enough to use IP country as a proxy for traffic being evil/legitimate) when traveling, but I often forget to turn off the VPN afterwards, and then spend the rest of my day browsing from my home IP (that terminates the VPN), which would have been hidden behind Private Relay if I'd actually been browsing from my home Wi-Fi.

Cross-site/app ad targeting getting creepy good despite using different browser profiles for work/personal browsing etc. is usually a good tell (at least on IPv6).

Re: IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

#34

Post by tredre3 »

dabbz wrote: post #12
exabrial wrote: post #4

Earlier quoted context omitted.

Yep, but one cannot script that, make it a part of a bash or automator actions, which is a problem.

There's a PLIST entry possibly relevant to it in `~/Library/Preferences/com.apple.networkserviceproxy.plist` I couldn't figure out how to get any changes to reflect but maybe it's a good pointer towards a solution? EDIT: Reading into this, looks like they're very intentional about not allowing arbitrary enable/disable calls to it, likely to prevent a hostile entity from switching it off on unsuspecting users. The sys…

> hostile entity from switching it off on unsuspecting users

I agree it's likely to prevent third parties from messing with the setting, but not hostile third parties specifically. Think of a VPN app or file sharing browser extensions who might want to disable the relay "to be helpful".

Because a truly hostile entity capable of changing local settings can already obtain the device's real IP and also capture traffic, the two things private relay is meant to prevent. There would be no point. If anything it might increase the odds of detection.

Re: IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

#35

Post by bernd289 »

There was at least one other Private Relay issue that doesn’t seem to have received much public attention.

I found and reported an IP leak to Apple in December 2025. The issue was caused by an EDNS Client Subnet (ECS) configuration problem in Akamai’s infrastructure, which could result in the client’s real IP being forwarded when it shouldn’t have been.

Apple confirmed the fix at the end of March 2026, and then I unexpectedly received a $5,000 Security Bounty in July.

Re: IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

#36

Post by acdha »

klausa wrote: post #16
TechRemarker wrote: post #3

Earlier quoted context omitted.

You can turn if off in settings > iCloud. Either temporary for a day and auto back on, or permanently until you turn it back on.

I desperately wish there was a "Turn off for five minutes, I'm dealing with dumb corpsec auth stuff" option.

On iOS: page menu —> kebab menu —> show IP address

Re: IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

#37

Post by xnyan »

tredre3 wrote: post #34
dabbz wrote: post #12

Earlier quoted context omitted.

There's a PLIST entry possibly relevant to it in `~/Library/Preferences/com.apple.networkserviceproxy.plist` I couldn't figure out how to get any changes to reflect but maybe it's a good pointer towards a solution? EDIT: Reading into this, looks like they're very intentional about not allowing arbitrary enable/disable calls to it, likely to prevent a hostile entity from switching it off on unsuspecting users. The sys…

> hostile entity from switching it off on unsuspecting users I agree it's likely to prevent third parties from messing with the setting, but not hostile third parties specifically. Think of a VPN app or file sharing browser extensions who might want to disable the relay "to be helpful". Because a truly hostile entity capable of changing local settings can already obtain the device's real IP and also capture traffic,…

Apple often plays a game where they blend security and business interests, but represent it only as a security interest.

They own the OS and could do for private relay like what they do for screen recording: when it's in use, overlay an unhideable visual indicator that it's that it's in use. Make it visually obvious when it turns off.

Re: IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

#39

Post by mysk »

Barbing wrote: post #38

Tommy Mysk, Talal Haj Bakry: how long did you wait after informing Apple of their incompetence before this public disclosure, please? Thank you for uncovering this and for the website proving the bug.

We didn't inform Apple at all. The reason why we didn't is explained here:

https://x.com/mysk_co/status/2085026605529768261

Glad you found the website helpful. Thank you.

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