With WebVPN, the VPN 3000 Concentrator can crash with the b_free assertion in buffer.c, line 435 message

[TCC_2]

Core issue

This issue is documented in Cisco bug ID CSCsb94643.

The crash dump analysis shows:

Address        function          file:line
000109E8       b_free            buffer.c:494
00010874       b_free            buffer.c:435
005F6BB8       p2IBDRelease      p2ibd.c:98
0003CFDC       sbdrop            sockutil.c:718
00042018       tcp_input         tcp_inpu.c:1551
00037E9C       ipProcLocalPkt    ipprrx.c:817
00037530       ipDoLocal         ipprrx.c:174
00036DF0       IpRtProcMsg       ip_task.c:287
00036B9C       IpRouterTask      ip_task.c:179

Resolution

The only workaround is to upgrade the VPN Concentrator software code to either 4.1.7.K or 4.7.2.E.