Hi! On Sun, 2022-08-28 at 14:40:44 +0200, Erik Auerswald wrote: > On Sat, Aug 27, 2022 at 07:37:15PM +0200, Erik Auerswald wrote: > > someone has described a remote DoS vulnerability in > > many telnetd implementations that I just happened to > > stumble over: > > > > https://pierrekim.github.io/blog/2022-08-24-2-byte-dos-freebsd-netbsd-telnetd-netkit-telnetd-inetutils-telnetd-kerberos-telnetd.html > > > > The vulnerability is a NULL pointer dereference when > > reading either of two two byte sequences: > > > > 1: 0xff 0xf7 > > 2: 0xff 0xf8 > > > > The blog shows GNU Inetutils' telnetd as vulnerable: > > > > https://pierrekim.github.io/blog/2022-08-24-2-byte-dos-freebsd-netbsd-telnetd-netkit-telnetd-inetutils-telnetd-kerberos-telnetd.html#remote-dos-inetutils
This has been assigned CVE-2022-39028 (I think from the Debian pool), after I reported it to the Debian security team. > > [...] > > In GNU Inetutils, the code lines to dereference table > > entries without first checking for NULL are in lines > > 321 and 323 of file "telnetd/state.c". The variable > > "ch" declared in line 315 of this file needs to be > > initialized to "(cc_t) (_POSIX_VDISABLE)", because it > > may not be assigned any value if the table is not yet > > initialized. > > > > References: > > > > line 315: > > https://git.savannah.gnu.org/cgit/inetutils.git/tree/telnetd/state.c#n315 > > line 321: > > https://git.savannah.gnu.org/cgit/inetutils.git/tree/telnetd/state.c#n321 > > line 323: > > https://git.savannah.gnu.org/cgit/inetutils.git/tree/telnetd/state.c#n323 > > > > I have attached a completely untested, not even compile > > tested, patch to do this (just the code changes, no NEWS > > or commit log or anything). Please test before committing. > > I have tested the patch now, it compiles and prevents the > crash by preventing the NULL pointer dereference. Thanks, I included this the other day in an upload to Debian sid, and I'm preparing updates for the Debian stable and oldstable releases too. Regards, Guillem