Re: [SECURITY] Out-of-Bounds Read in MPLS Extension Parsing — traceroute 2.1.2

[Ellenor Bjornsdottir <ellenor/securesoftware () umbrellix net>]

FYI:

As Alan Coopersmith just said, oss-security is a public mailing list.
You would need to have emailed only individual persons and private
mailing lists (like secalert () redhat com and Mr Butskoy) related to the
development and distribution of the program in question for this to
have been coordinated disclosure. The public message to
oss-security () lists openwall com would then need to be posted in July,
not this month.

Remember that for the next vulnerability you try to do coordinated
disclosure for.

On Tue, 28 Apr 2026 23:03:58 +0100
MOHAMED AZIZ RAHMOUNI <mohamedaziz.rahmouni () insat ucar tn> wrote:

> Hello,
>
> I am reporting a security vulnerability I discovered in traceroute
> 2.1.2 during manual code review and dynamic fuzzing.
>
> Summary:
> An out-of-bounds read exists in traceroute/traceroute.c. After
> recvmsg() returns, bufp is advanced past the IPv4 header (bufp +=
> hlen) but n is not decremented accordingly. The subsequent call:
>
>     handle_extensions(pb, bufp + offs, n - offs, step);
>
> passes a len value that is hlen bytes (20 for IPv4, 40 for IPv6)
> larger than the actual data available from bufp + offs. This causes
> the MPLS extension parser to read past the received packet boundary
> into uninitialized stack memory within buf[1280].
>
> The vulnerability is remotely triggerable by any on-path network
> device that can send a crafted ICMP Time Exceeded response with MPLS
> extensions to a traceroute -e invocation. I have confirmed the issue
> with a working proof of concept.
>
> Proposed fix (single line addition after line 1427):
>
>     bufp += hlen;
>     n -= hlen;   // add this line
>
> I have attached a full technical report including root cause analysis,
> proof of concept code, memory layout analysis, and impact assessment.
>
> Please confirm receipt of this report.
>
> Regards,
> Security researcher Zyyz
>
> Mohamed Aziz Rahmouni



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