Critical Start security expert Russell Sanford discovered and reported two critical zero-day vulnerabilities in the Sophos Web Appliance in December of 2016. The vulnerabilities, documented under CVE-2016-9553, allow the remote compromise of the appliance’s underlining Linux subsystem. The vulnerabilities have now been patched in the January 2017 4.3.1 release of the appliance line.
Here is a summary of the two vulnerabilities documented under CVE-2016-9553.
The Sophos Web Appliance (version 126.96.36.199) is vulnerable to two Remote Command Injection vulnerabilities affecting its web administrative interface. These vulnerabilities occur in the MgrReport.php (/controllers/MgrReport.php) component responsible for blocking and unblocking IP addresses that are able to access appliance.
The device doesn’t properly escape the information passed in the variables ‘unblockip’ and ‘blockip’ before calling the shell_exec() function which allows for system commands to be injected into the device.
The page that contains the vulnerabilities, /controllers/MgrReport.php, is accessed by a number of the machine’s built in commands in administrative interface. The pages that call to the vulnerable page (passed in the ‘&c=’ parameter) are: ‘report’, ‘trend_volume’, ‘trend_suspect’,’top_app_ctrl’, ‘perf_latency’, ‘perf_throughput’, ‘users_browse_summary’, ‘traf_sites’, ‘traf_blocked’, ‘traf_users’, ‘users_virus_downloaders’, ‘users_pua_downloaders’, ‘users_highrisk’, ‘users_policy_violators’, ‘users_top_users_by_browse_time’, ‘users_quota’, ‘users_browse_time_by_user’, ‘users_top_users_by_category’, ‘users_site_visits_by_user’, ‘users_category_visits_by_user’, ‘users_monitored_search_queries’, ‘users_app_ctrl’, ‘traf_category’, ‘traf_download’, and ‘warned_sites’.
Exploitation of this vulnerability yields shell access to the remote machine under the system account ‘spiderman’.
Sophos has issued an update to correct this vulnerability. More details can be found at:
This vulnerability was discovered by Russell Sanford of Critical Start.
CVSS Base Score: 8.5
CVSS v2 Vector: (AV:N/AC:M/Au:S/C:C/I:C/A:C/E:F/RL:OF/RC:C/CDP:ND/TD:ND/CR:H/IR:H/AR:ND)
Web Appliance before version 188.8.131.52
2016-11-12 – Vulnerability discovered in audit
2016-11-13 – POC exploit created
2016-11-19 – Contacted MITRE for CVE
2016-11-22 – CVE-2016-9553 assigned
2016-11-29 – Sophos Contacted through Bugcrowd to coordinate fix
2017-01-20 – Sophos patched bug in Version 4.3.1 (Work Order# NSWA-1258)
2017-01-20 – Coordinated public release of advisory
2017-01-28 – CVE-2016-9553 publicly released.
About Critical Start
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