O2 VoLTE: locating any customer with a phone call
mastdatabase.co.uk> Attempts were made to reach out to O2 via email (to both Lutz Schüler, CEO and securityincidents@virginmedia.co.uk) on the 26 and 27 March 2025 reporting this behaviour and privacy risk, but I have yet to get any response or see any change in the behaviour.
This is really poor. And why is a Virgin Media address the closest best thing here? https://www.o2.co.uk/.well-known/security.txt should 200, not 404.
To be clear, I have no problem with disclosure in these circumstances given the inaction, but I'm left wondering if this is the sort of thing that NCSC would pick up under some circumstances (and may have better luck communicating with the org)?
This one is actually on us. The email contacted was actually @virginmediao2.co.uk, not @virginmedia.co.uk. It's a typo in the article.
I'll update it with a correction.
I have spotted another error:
> is within LAC 0x1003 (decimal: 4009)
It should be decimal 4099.
How did you spot that?
When you’ve been working with computers for long enough, the powers of 2 live in your head… and there’s no way 0x1000 is less than 4096 :)
I did the conversion in my head as I was reading.
Oops. Thanks.
There are several email addresses listed in the privacy policy (a GDPR requirement). Maybe somebody is listening there. E.g. DPO@o2.com
You could file an SAR with them to find out what they’re doing internally with anything with your name linked to it. Might also be preemptively contacting https://www.openrightsgroup.org/ to get the narrative on your side, in case they come knocking with the CMA.
O2 used to have a responsible disclosure address - but they removed it a few years back.
When I worked there (many years ago) the security team was excellent. When I emaileld them about an issue last year, they were all gone.
We know the relevant team within O2 was actually informed, but evidently no action (or insufficient action) was taken.
The really interesting part of this issue is, that under most jurisdictions it probably won't even qualify as hacking. The data is sent out by the network voluntarily and during normal use.
There are no systems at any point tricked into revealing personal data, which is often illegal, even if the hack is trivial. Even appending something like "&reveal_privat_data=true" to an URL might be considered illegal, because there is clear intent to access data you shouldn't be allowed to access. In this case none of that is done.
It is, however, a data breach, triggering the requirement for them to report it to the regulator immediately or get fined, etc etc (if such rules exist in the UK)
I suppose even if O2 isn't in EU jurisdiction they could apply pressure since the example showed a Denmark customer being impacted. Maybe that telco in Denmark can't peer with O2 if O2 can't secure their EU customers data.
> The really interesting part of this issue is, that under most jurisdictions it probably won't even qualify as hacking
You clearly aren’t familiar with how broad the Computer Misuse Act is
> You clearly aren’t familiar with how broad the Computer Misuse Act is
No, I'm not familiar with it at all. But usually illegal hacking requires to access devices in a way you aren't allowed to access. As long as making the phone call itself is not an issue, it should be fine. Dumping data from the memory of your phone can't be unauthorized.
It would probably become an issue if you make unusual phone calls, harassing people with constantly calling, or calling just for the purpose of getting the location data and immediately hanging up. But just dumping the diagnostics for regular phone calls should be fine (I'm not a lawyer).
> Dumping data from the memory of your phone can't be unauthorized.
> just dumping the diagnostics for regular phone calls should be fine
IANAL, but computer hacking laws like the CMA in the UK and CFAA in the US are written in a manner so vague that even pressing F12 to view the source of a web page could be a violation [0]. From O2's perspective, they could argue that the OP has accessed their internal diagnostic data in an unauthorized manner. What we (technical people) think is irrelevant.
[0]: In the US, the DOJ has revised its policy to not prosecute defendants pursuing "good faith security research," which you may trust at your own risk: https://www.justice.gov/archives/opa/pr/department-justice-a...
I don't have a lot of knowledge about US and UK law, but I hear a lot of bad things.
"good faith security research" is a different ballpark though. Some laws catch all unauthorized access, even if the intent is not in a bad faith (which is probably a very bad idea, but that's how it is). But it also makes sense to some point: if your neighbor has a really bad lock that can be opened just by hitting the door frame a few times, you're also not allowed to break in just to disclose their bad security.
Usually some deliberate action needs to be taken that qualifies as unauthorized access. Something like adding a malformed header to a HTTP request could be enough. Or logging in with credentials that are clearly not yours (even if it's just admin/admin). But logging the traffic of regular and authorized usage patterns shouldn't be enough.
Legally, using any tool that allows you to view raw cellphone traffic from your own phone is already unauthorized access (probably).
Famously, in Germany, it's illegal to be carrying a laptop on which nmap is installed. Everyone (who has a laptop and knows how to use nmap) still does it. It's one of those crimes which they get you for if they don't like you but you didn't commit any actual crime.
It's tough, but when the people don't respond what do you do?
Do you just sit on the info, hoping noone else sees it and exploits it?
Or do you try and get them to fix it somehow?
First of all, thank you for trying to resolve this with the carrier and finally bringing it up to everyone's attention here. Perhaps public attention is what's needed to push them to address the problem.
To be honest, I personally would be scared to report such vulnerabilities with my real identity to begin with. With big tech companies, no matter how poorly their bug bounty programs are run, I still have this naive expectation that they won't shoot the messenger. At worst they could ban my accounts and maybe send threatening letters, but they probably won't ruin my life as long as I abide by the norms (agreed by technical people).
However, I do not feel the same naive optimism towards "legacy" institutions like telecoms and public services. At best it's thankless work, at worst I get sued [0] or become a scapegoat so some official could score some political points [1]. It's unfortunate - I am acutely aware that this is chilling effect at work, and our systems are collectively less secure because of it.
[0]: https://www.cnbc.com/2024/09/15/dark-web-expert-warned-us-ho... [1]: https://techcrunch.com/2021/10/15/f12-isnt-hacking-missouri-...
Being a customer yourself, I guess you could sue them
The wild part: this isn’t a theoretical bug. It’s implementation laziness that other UK networks already solved, as the post notes. ECI leaks have been called out since LTE rolled out—see papers like https://arxiv.org/abs/2106.05007—and automated location mapping is trivial given open mast DBs.
Probably panicking and waiting to be told what to do by the security services that have been using this.
All of the information leaked in the headers is already readily available through lawful interception.
Also very curious how the call initiator was able to see the call control messages (ie SIP). Arent all these messages wrapped inside an encrypted GRE tunnel between handset and cell tower (and MME)? Being able to unpick GRE tunnel encryption would be a gigantic hole. Perhaps this only works because the OP is running analysis on their device, but even then I'm surprised that the pre-encryption payload is available.
Hello, article editor here. Many Android devices with Qualcomm chips offer the option to expose a modem diagnostics port over USB meaning a rooted device isn't even needed. It's just much easier to use NSG rooted on-device than going around with a laptop places.
It's as simple as using Scat (https://github.com/fgsect/scat) with the modem diag port enabled to view all signalling traffic to/from the network.
They're using a rooted Android phone and an app called Network Signal Guru: https://play.google.com/store/apps/details?id=com.qtrun.Quic...
At least the free version of the app doesn't seem to "decrypt" anything, but it has root access and access to the modem, so it can read these logs. It can also disable bands and try to lock to a specific mast (like dedicated 4G/5G routers can), which is useful if you're trying to use mobile data as your main internet connection.
Right, so, that's the hacking tool they'll soon get prosecuted for using, while the problem will remain unfixed.
Many operators do configure the SIP signaling for VoLTE to use an IPsec transport terminated at the P-CSCF, but most (if not all) of them only configure IPsec to provide integrity protection.
i think you meant GTP tunnel. And GTP tunnel is between enodeb and core network. it's secured only in case that it run inside IPSEC.
Doh! Yes, of course. Thank you
^^edit: GTP.
O2 has claimed that the problem is now fixed: https://www.ispreview.co.uk/index.php/2025/05/o2-uk-fixes-vo...
The submitted post was updated this morning
>O2 reached out to me via email to confirm that this issue has been resolved. I have validated this information myself, and can confirm that the vulnerability does appear to be resolved.
From their statement "Our engineering teams have been working on and testing a fix for number of weeks". Can you image if a database was knowingly left unsecured for that long with data that sensitive and seemingly without telling anyone. It will be interesting to see how the ICO deal with this.
Seems to be a serious problem. It's not that hard to root a phone, install NSG, and look at this info. O2 is also the largest mobile network in the UK and they have contracts with the government...
It's disappointing that they didn't reply, but I'm not surprised. O2 seems to be a mess internally. Anything that can't be fixed by someone at a store takes ages to fix (eg: a bad number port). Their systems seem to be outdated, part of their user base still can't use VoLTE, their new 5G SA doesn't support voice and seems to over rely on n28 making it slow for many, their CTO blogs about leaving "vanity metrics behind"[0] even though they are usually the worst network for data, etc.
[0] https://news.virginmediao2.co.uk/leaving-the-vanity-metrics-...
I’m starting to think the reason they don’t charge for EU roaming is because they don’t have a system to do it.
I’m not sure how O2 are still in business - they’re the worst network by far, even Three with their diabolical backhaul situation is better. Only reason I have an O2 SIM along with my EE one is for Priority tickets/signal inside their venues
They've got a lot better if you have access to their 5G Standalone network. But it does require a new SIM card + compatible phone. It's night and day...
So giffgaff,who also use the O2 network, claim that they are unaffected as they have their own implementation of the service on top of O2s physical network. Which might be true, but I'm a bit suspicious as I know they are actually owned by the same company now,so consolidation is likely. If anyone tries replicating this on a giffgaff sim it would be good to know the result...
They've been owned by Telefónica for a while. IIRC Telefónica acquired O2 in 2006, and launched Giffgaff as a new brand in 2009.
I've tested this on the giffgaff network, and it does have an impact. I'm not sure how they came to a different conclusion.
Could you mitigate this by turning off VoLTE? I can see docs online for turning it off on an iPhone 11 - but my iPhone 15 doesn't have that option!
> Disabling 4G Calling does not prevent these headers from being revealed, and if your device is ever unreachable these internal headers will still reveal the last cell you were connected to and how long ago this was.
So it seems like that won't do anything.
One annoyance with O2 UK is that they don't support VoLTE for legacy pay-as-you-go customers, only pay-monthly. Now I'm actually kind-of glad for that.
Coming second half of this year!
Cool, hopefully before their wide-scale 3G switch-off starting August.
I don’t know anything about IMS but I assume they have to stay on the call long enough for the debug headers to be sent (like the tracing the call thing in every spy movie but real) and if that’s the case can this be mitigated by “just”* not answering calls from unknown numbers?
*yes I’m aware that means people you know who have your number could also exploit this
I guess this information is already known to the network before the connection is even established. Those seem to be debugging headers, you probably need them for cases where the connection can't be established properly to debug why. If I understand the article correctly, the information is even there if the receiving phone is turned off, then you get the last known cell.
IMS is just SIP core + bunch of gateways + integration with base LTE infra (eNodeB, PCRF, etc) so "signaling messages" are just SIP messages. So depending on whether those compromising headers were included on things like SIP 180 Ringing messages and such it may not be enough to not answer the calls. Source: actually worked on deploying IMS at a telco (not this one)
The headers are included in every single downlink message after initiating a call, including the downlink SIP Invite message before 100 Trying, 180 Ringing or 183 Session Progress.
If you're quick enough (or automate this with dedicated software, like an attacker might actually do), it won't even need to ring out. It's really not good.
that's wild. did you also try any callees connected to a different PLMN?
I’m curious to see if this exists on O2 in NZ. I switched to them last week because they do free roaming in Australia, and VoLTE calls.
I doubt it. This is likely O2 UK specific.
This only affects O2, not EE/VF/3, right?
According to GDPR this is clearly illegal. I am pretty sure their subscriber contracts don't contain consent for sharing your location to any caller.
Now UK has left the EU so GDPR does no longer apply. But it is my understanding they have not changed any fundamental principles in whatever applies now?
I'm no expert, but I'm fairly sure that UK GDPR applies, which is effectively the same as the EU version https://ico.org.uk/for-organisations/data-protection-and-the...
Yes, it still exists. Most (all?) EU legislation that ended had to be explicitly revoked, since the UK was fairly diligent in transposing it to national legislation.