Re: [PATCH 1/1] net/ipv4: discard icmp timestamp requests

[Ido Schimmel <idosch@nvidia.com>]

On Thu, Jul 23, 2026 at 05:37:50PM +0100, John Haxby wrote:
> In fact, there is a reason to revisit this.  CVE-1999-0524 went from having a CVSS score of 0.0 (ie not a vulnerability) to CVSS2 score 2.1 in 2022 and today it has a CVSS3.x score of 4.0.   Those first two links are messages in 2019, well before there was a non-zero score.  The last link is, admittedly, 2024 but rather than completely removing ICMP timestamp (as was done with ICMP address, the other part of CVE-1999-0524) is provides a sysctl to turn it off.   I wasn't aware of that possible patch, but it assumes that there's a use-case for ICMP timestamp and in the few years I've been aware of this as an issue (in my previous job) I haven't found one.

You didn't provide any new technical arguments that weren't already
discussed in the past and rejected. The premise that the time of day is
sensitive information was rejected there. Re-scoring of the CVE is not a
good enough argument to drop this functionality from the kernel and
potentially introduce a regression for some users.

> 
> Admittedly, it's easy to just disable the timestamp in a firewall (eg firewall-cmd --add-icmp-block=timestamp-request) but people have to discover that after a scanner has screamed warnings about unfixed vulnerabilities.  So now I have actual time on my hands not dealing with the daily firefight of kernel CVEs, I had time to actually do something about this that's been annoying me and quite a lot of other people -- I mentioned googling for "CVE-1999-0524 fix".

There is even less of a reason to remove this functionality when the
"fix" is widely known and easy to implement. Not everything needs to be
solved in the kernel, even if it's easier for some users.

> 
> If there's a genuine use-case for ICMP timestamp, then yes, it should stay and we'll just add to the documentation from Cisco, f5, Dell, Oracle, etc to explain how to disable it if you don't have that use case.  But lacking a use-case, I still think ICMP timestamp should simply be consigned to the bin.

We have no way of knowing who is using this feature and I don't think we
should remove it when the reason is effectively reduced to "pleasing
some scanners".