A few days ago this happened on multiple Centos 5 servers and apparently anyone using rpmforge was affected by this error and there was no solution other than disabling that repo to fix it.
To some this highlighted a few points, that there is a reason RHEL exists with full paid support, and also that this could be a vulnerability and huge flaw with yum. A yum search or install should not segfault just because the rpmforge repo goes down.
Fortunately it came back up as expected but it was definitely an inconvenience for many and hopefully a lesson learned by everyone including the yum devs
rpmforge: [#### ] 471/10722Segmentation fault
yum: segfault at 0000000000000000 rip 00002ade62153a30 rsp 00007fff76f9fe58 error 4