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Are Verizon customer routers vunerable to the glibc bug (CVE-2015-7547)?

Are Verizon customer routers vunerable to the glibc bug (CVE-2015-7547)?

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Contributor dlc_usa
Contributor
Posts: 5
Registered: ‎02-17-2016
Message 1 of 8
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If so, is Verizon going to harden these units expeditiously?

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Platinum Contributor III Platinum Contributor III
Platinum Contributor III
Posts: 7,767
Registered: ‎11-04-2008

Hard to say.

But this is a Linux bug. Not sure how that affects the router.


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Contributor dlc_usa
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Posts: 5
Registered: ‎02-17-2016

Most home routers are based on the Linux kernel (certainly the Actiontecs are) and usually use a lot of the GNU infrastructure, too.  The real question is are they using glibc or something else like uclibc.

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Contributor dlc_usa
Contributor
Posts: 5
Registered: ‎02-17-2016

It may be possible to filter using iptable rules according to the announcement:

 

Mitigating factors for UDP include:
- A firewall that drops UDP DNS packets > 512 bytes.
Mitigating factors for TCP include:
- Limit all replies to 1024 bytes.

This should catch any serious stack overflowing cracking attempts.  If would good for Verizon to tell their customers how to implement such rules.  Of course, they could add such rules to their customer-facing routers as an alternative, I expect, but they should tell us if they are.

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Copper Contributor pa28pilot
Copper Contributor
Posts: 22
Registered: ‎06-21-2011

The problem with those suggested mitigations is that they're essentially requiring the user to avoid any DNS resolvers that provide responses using the Extension Mechanisms for DNS, which translates to pretty much any of those that are useful for zones protected with DNSsec signatures.

 

It may be moot for many FiOS users, as it appears that VZ's name servers don't properly handle large replies right now anyway.  You can see for yourself if you check them with OARC's DNS Reply Size Test Server.

 

So basically the user's choice is to either use resolvers that allow zones to be spoofed or to use resolvers that might send an answer that overflows a buffer. 

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Contributor dlc_usa
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Posts: 5
Registered: ‎02-17-2016

Dang.  Well, maybe Verizon will chime in here.  Thank you, Cherokee commander.

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Platinum Contributor III Platinum Contributor III
Platinum Contributor III
Posts: 4,437
Registered: ‎12-16-2012

Verizon will never chime in.

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Contributor dlc_usa
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Posts: 5
Registered: ‎02-17-2016
Message 8 of 8
(878 Views)

I was given the number for expert service to inquire if glibc is deployed, but I'm not certain it's worth the time.

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