C2/B2-Series f/w 5.02.14.0002 Reboots with "sshd_undoquit / kex_dh_hash" Backtraces in Log

[FAQ_User]

Article ID: 14479

Products
C2-Series, firmware 5.02.10.0003 through 5.02.17.0006
B2-Series, firmware 4.02.10.0003 through 4.02.17.0006

Changes
Attempted an SSH management session from linux SSH client version OpenSSH_5.9p1, OpenSSH_6.2p2, or OpenSSH_6.2p3.

Symptoms
Unit lockup, then reset.
Diagnostics include "

code:

sshd_undoquit

" and "

code:

kex_dh_hash

" BackTraces seen in the current.log (5487).

For example:<57> FEB 14 16:46:04 2012 STK1 BOOT[268430848]: bootos.c(1338) 22 %%
Start of Code - Build:04.02.10.0003 Date:Tue Aug 24 10:09:03 2010
BackTrace-0x00022928: sysReboot (0x22928) + 0x0
BackTrace-0x000318a8: SwitchReset (0x31800) + 0xa8
BackTrace-0x0002a728: log_error_nvram (0x2a62c) + 0xfc
BackTrace-0x00044534: osapiMalloc_track (0x44354) + 0x1e0
BackTrace-0x00cdead4: buffer_expand (0xcdea1c) + 0xb8
BackTrace-0x00cdedd4: buf_put_nbytes (0xcdeda4) + 0x30
BackTrace-0x00d1c21c: kex_dh_hash (0xd1c130) + 0xec
BackTrace-0x00d17fd4: v2ssh_init_transport (0xd128b4) + 0x5720
BackTrace-0x00d15edc: v2ssh_init_transport (0xd128b4) + 0x3628
BackTrace-0x00cf1648: dispatch_v2_server_msg (0xcf0dec) + 0x85c
BackTrace-0x00d0ea68: ssh_recv_thread (0xd0e194) + 0x8d4
BackTrace-0x00ce866c: sshd_undoquit (0xce7c3c) + 0xa30
BackTrace-0x00ce89cc: sshd_undoquit (0xce7c3c) + 0xd90
BackTrace-0x01094780: vxTaskEntry (0x1094718) + 0x68
BackTrace-symbol not found for 0x0
<110> FEB 14 16:46:34 2012 STK1 BOOT[203871872]: edb_bxs.c(948) 38 %%
Last switch reset caused by osapi.c(1168): Error code 0x002a5000,
after 12383112 secondCause
During the key exchange init process, the unit freezes and resets due to non-availability of memory.

Solution/Workaround
For the C2, upgrade to firmware 5.02.18.0002 or higher.
For the B2, upgrade to firmware 4.02.18.0002 or higher.
Version x.02.15.0002 release notes state, in the '

code:

Firmware Changes and Enhancements

' section:

code:

16248

code:

Addressed an issue whereby logging to the switch via OpenSSH_5.9p1 SSH client could potentially cause the unit to lock up or reset.

Version x.02.18.0002 release notes state, in the '

code:

Firmware Changes and Enhancements

' section:

code:

18575

code:

Corrected an interoperability issue with Openssh-client 1:6.2p2-3, that caused the switch to hang. This SSH client incorrectly has Clientkex length as a negative value. This client will not be supported.

Workaround: Upon new error message "

code:

hash mismatch - key_verify failed for server_host_key

", use a different SSH Client application or version.