CVE-2017-15705 Information

Description

A denial of service vulnerability was identified that exists in Apache SpamAssassin before 3.4.2. The vulnerability arises with certain unclosed tags in emails that cause markup to be handled incorrectly leading to scan timeouts. In Apache SpamAssassin using HTML::Parser we setup an object and hook into the begin and end tag event handlers In both cases the \open\ event is immediately followed by a \close\ event - even if the tag does not close in the HTML being parsed. Because of this we are missing the \text\ event to deal with the object normally. This can cause carefully crafted emails that might take more scan time than expected leading to a Denial of Service. The issue is possibly a bug or design decision in HTML::Parser that specifically impacts the way Apache SpamAssassin uses the module with poorly formed html. The exploit has been seen in the wild but not believed to have been purposefully part of a Denial of Service attempt. We are concerned that there may be attempts to abuse the vulnerability in the future.

CVSS Vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Reference

http://lists.opensuse.org/opensuse-security-announce/2019-08/msg00002.html http://www.securityfocus.com/bid/105347 https://access.redhat.com/errata/RHSA-2018:2916 https://lists.apache.org/thread.html/7f6a16bc0fd0fd5e67c7fd95bd655069a2ac7d1f88e42d3c853e601c@3Cannounce.apache.org3E https://lists.debian.org/debian-lts-announce/2018/11/msg00016.html https://security.gentoo.org/glsa/201812-07 https://usn.ubuntu.com/3811-1/ https://usn.ubuntu.com/3811-2/

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

LOW

Base Severity

5.3