Internet Bug Bounty: Exim use-after-free vulnerability while reading mail header involving BDAT commands

Original article is here Use-after-free in receivemsg leads to RCE Vulnerability Analysis To explain this bug, we need to start with the memory management of exim. There is a series of functions starts with store such as storeget, storerelease, storereset. These functions are used to manage...

Exim 4.89 - 'BDAT' Denial of Service(CVE-2017-16944)

On 23 November, 2017, we reported two vulnerabilities to Exim. These bugs exist in the SMTP daemon and attackers do not need to be authenticated, including CVE-2017-16943 for a use-after-free UAF vulnerability, which leads to Remote Code Execution RCE; and CVE-2017-16944 for a Denial-of-Service D...

UBUNTU-CVE-2017-16944

The receivemsg function in receive.c in the SMTP daemon in Exim 4.88 and 4.89 allows remote attackers to cause a denial of service infinite loop and stack exhaustion via vectors involving BDAT commands and an improper check for a '.' character signifying the end of the content, related to the...

Exim 4.89 Denial Of Service

While parsing BDAT data header, exim still scans for '.' and consider it the end of mail. https://github.com/Exim/exim/blob/master/src/src/receive.cL1867 Exim goes into an incorrect state after this message is sent because the function pointer receivegetc is not reset. If the following command is...

exim -- remote code execution, deny of service in BDAT

Exim team reports: The receivemsg function in receive.c in the SMTP daemon in Exim 4.88 and 4.89 allows remote attackers to execute arbitrary code or cause a denial of service use-after-free via vectors involving BDAT commands...