Format string vulnerability in the dkimeximverifyfinish function in src/dkim.c in Exim before 4.76 might allow remote attackers to execute arbitrary code or cause a denial of service (daemon crash) via format string specifiers in data used in DKIM logging, as demonstrated by an identity field containing a % (percent) character.

The openlog function in log.c in Exim 4.72 and earlier does not check the return value from (1) setuid or (2) setgid system calls, which allows local users to append log data to arbitrary files via a symlink attack.

The dmarcprocess function in dmarc.c in Exim before 4.82.1, when EXPERIMENTALDMARC is enabled, allows remote attackers to execute arbitrary code via the From header in an email, which is passed to the expandstring function.

As reported to the exim user's mailing list [1], Exim suffers from a local vulnerability where a string expansion is evaluated twice. If a local attacker were able to provide unsanitized data to a data source used by Exim for looking up a value, in certain situations, the data would be eval()'d twice. This is not remotely exploitable and requires a user account on the Exim server, and an Exim configuration that does lookups against files to which the user has edit access. The end result is that, if the conditions are true, arbitrary code could be executed as the exim user. As described in the posting:

""" The root cause of this issue is the arguments to mathematical comparison operations are expanded twice (<, <=, >, >=, =). The intent of the original code was the first expansion could (for example) lookup an item from a file. The assumption was that entry would be some form of valid integer so that value was then passed to the expand function again to do a numeric conversion of values such as 19k or 45M to integers. However, if the content of the lookup is under direct user control, they could insert something with an expansion, such as:

${run {/bin/touch /tmp/OUCH}}

Since the data is not sanitized when the second expansion occurs (intended to process numerical conversion), that command would get executed as the exim user. """

This is corrected in the Exim 4.83 release [2],[3],[4]. From the description, it looks as though every version of Exim released since 2004 is affected.

[1] https://lists.exim.org/lurker/message/20140722.152452.d6c019e8.en.html [2] http://git.exim.org/exim.git/blob/exim-483:/doc/doc-txt/ChangeLog [3] http://git.exim.org/exim.git/commitdiff/7685ce68148a083d7759e78d01aa5198fc099c44 [4] http://git.exim.org/exim.git/commitdiff/0de7239e563eff6e83c3e72d7deb9fd26a54a3a7

Exim 4 before 4.94.2 allows Integer Overflow to Buffer Overflow because getstdinput allows unbounded reads that are accompanied by unbounded increases in a certain size variable. NOTE: exploitation may be impractical because of the execution time needed to overflow (multiple days).

Exim 4 before 4.94.2 has Improper Neutralization of Line Delimiters. An authenticated remote SMTP client can insert newline characters into a spool file (which indirectly leads to remote code execution as root) via AUTH= in a MAIL FROM command.

Exim 4 before 4.94.2 has Improper Restriction of Write Operations within the Bounds of a Memory Buffer. This occurs when processing name=value pairs within MAIL FROM and RCPT TO commands.

Exim 4 before 4.94.2 allows Out-of-bounds Read. smtpsetupmsg may disclose sensitive information from process memory to an unauthenticated SMTP client.

Exim 4 before 4.94.2 allows Heap-based Buffer Overflow in queuerun via two sender options: -R and -S. This may cause privilege escalation from exim to root.

Exim 4 before 4.94.2 allows Execution with Unnecessary Privileges. The -oP option is available to the exim user, and allows a denial of service because root-owned files can be overwritten.

Exim 4 before 4.94.2 allows Out-of-bounds Write because the main function, while setuid root, copies the current working directory pathname into a buffer that is too small (on some common platforms).

Exim 4 before 4.94.2 allows an off-by-two Out-of-bounds Write because "-F ''" is mishandled by parsefixphrase.

Exim 4 before 4.94.2 allows Buffer Underwrite that may result in unauthenticated remote attackers executing arbitrary commands, because smtpungetc was only intended to push back characters, but can actually push back non-character error codes such as EOF.

Exim 4 before 4.94.2 allows Execution with Unnecessary Privileges. Because Exim operates as root in the spool directory (owned by a non-root user), an attacker can write to a /var/spool/exim4/input spool header file, in which a crafted recipient address can indirectly lead to command execution.

Exim 4 before 4.94.2 allows Execution with Unnecessary Privileges. Because Exim operates as root in the log directory (owned by a non-root user), a symlink or hard link attack allows overwriting critical root-owned files anywhere on the filesystem.

Exim 4 before 4.94.2 allows Heap-based Buffer Overflow because it mishandles "-F '.('" on the command line, and thus may allow privilege escalation from any user to root. This occurs because of the interpretation of negative sizes in strncpy.

Exim 4 before 4.94.2 has Improper Neutralization of Line Delimiters. Local users can alter the behavior of root processes because a recipient address can have a newline character.

Exim 4 before 4.92 allows Integer Overflow to Buffer Overflow, in which an unauthenticated remote attacker can execute arbitrary code by leveraging the mishandling of continuation lines during header-length restriction.

Exim 4 before 4.94.2 allows Out-of-bounds Read because pdkimfinishbodyhash does not validate the relationship between sig->bodyhash.len and b->bh.len; thus, a crafted DKIM-Signature header might lead to a leak of sensitive information from process memory.

Exim 4 before 4.94.2 allows Exposure of File Descriptor to Unintended Control Sphere because rdainterpret uses a privileged pipe that lacks a close-on-exec flag.

Exim 4 before 4.94.2 has Improper Neutralization of Line Delimiters, relevant in non-default configurations that enable Delivery Status Notification (DSN). Certain uses of ORCPT= can place a newline into a spool header file, and indirectly allow unauthenticated remote attackers to execute arbitrary commands as root.