{"id":55921,"date":"2020-02-01T00:00:00","date_gmt":"2020-01-31T21:00:00","guid":{"rendered":"https:\/\/prohoster.info\/blog\/blog_prohoster\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os"},"modified":"2020-02-18T14:04:05","modified_gmt":"2020-02-18T11:04:05","slug":"root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/root-uyazvimost-v-sudo-zatragivayushhaya-linux-mint-i-elementary-os","title":{"rendered":"Root vulnerability in sudo affecting Linux Mint and Elementary OS","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

In the utility sudo<\/a><\/noindex>, used to facilitate command execution on behalf of other users, identified<\/a><\/noindex> vulnerability (CVE-2019-18634<\/a><\/noindex>), which allows privilege escalation to the root user. The issue appears starting from sudo version 1.7.1 only when using the 'pwfeedback' option in the \/etc\/sudoers file, which is disabled by default but enabled in some distributions like Linux Mint and Elementary OS. The problem has been resolved in the release sudo 1.8.31<\/a><\/noindex>, published a few hours ago. The vulnerability remains unpatched in these distributions.<\/p>\n

The 'pwfeedback' option enables displaying the '*' character after each entered character when typing a password. Due to an error<\/a><\/noindex> the implementation of the getln() function defined in the tgetpass.c file, a string with an excessive length passed through standard input (stdin) may not fit in the allocated buffer under certain conditions, leading to overwriting other data on the stack. The overflow occurs during the execution of sudo code with root privileges.<\/p>\n

The essence of the problem lies in the fact that when using the special character ^U (clear line) during input and in case of a recording operation failure, the code responsible for clearing the displayed '*' characters resets the buffer's available size information but does not return the current position pointer in the buffer to its original value. Another factor contributing to the exploitation is the lack of automatic disabling of the 'pwfeedback' mode when data is received not from a terminal but through the input stream (this oversight creates conditions for a recording error, for example, on one-way systems. unnamed pipes<\/a><\/noindex> the error occurs when attempting to write past the end of the reading pipe).<\/p>\n

Since the attacker can completely control the data overwrite in the stack, creating an exploit that allows privilege escalation to the root user is not difficult. The issue can be exploited by any user, regardless of permissions to use sudo and specific user configurations in sudoers. To block the issue, ensure that the 'pwfeedback' setting is absent in \/etc\/sudoers and disable it if necessary ('Defaults !pwfeedback'). To check for the existence of the issue, you can execute the code:<\/p>\n

$ perl -e 'print(('A' x 100 . '') x 50)' | sudo -S id
\n Password: Segmentation fault<\/p>\n

<\/a><\/noindex><\/p>\n

Source: opennet.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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[…]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-55921","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Root vulnerability in sudo affecting Linux Mint and Elementary OS | ProHoster","description":"In the sudo utility, used to organize the execution of commands on behalf of other 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