CVE-2015-5600
HighSummary
The kbdint_next_device function in auth2-chall.c in sshd in OpenSSH through 6.9 does not properly restrict the processing of keyboard-interactive devices within a single connection. This allows remote attackers to conduct brute-force attacks or cause denial of service via a long and duplicative list in the ssh -oKbdInteractiveDevices option.
Risk Assessment
Attackers can exploit this vulnerability to increase CPU load on the server or gain access to the system through brute-force attacks, potentially leading to serious security implications for the organization.
Recommendation
It is recommended to update OpenSSH to the latest version to mitigate this vulnerability and to restrict the use of the KbdInteractiveDevices option to trusted devices.
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OpenSSH 5.6 and earlier, when J-PAKE is enabled, does not properly validate the public parameters in the J-PAKE protocol. This allows remote attackers to bypass the need for knowledge of the shared secret and successfully authenticate by sending crafted values in each round of the protocol.
Original NVD description (English source)
The kbdint_next_device function in auth2-chall.c in sshd in OpenSSH through 6.9 does not properly restrict the processing of keyboard-interactive devices within a single connection, which makes it easier for remote attackers to conduct brute-force attacks or cause a denial of service (CPU consumption) via a long and duplicative list in the ssh -oKbdInteractiveDevices option, as demonstrated by a modified client that provides a different password for each pam element on this list.