Vulnerability CVE-2017-15705


Published: 2018-09-17

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.

Type:

CWE-20

(Improper Input Validation)

CVSS2 => (AV:N/AC:L/Au:N/C:N/I:N/A:P)

CVSS Base Score
Impact Subscore
Exploitability Subscore
5/10
2.9/10
10/10
Exploit range
Attack complexity
Authentication
Remote
Low
No required
Confidentiality impact
Integrity impact
Availability impact
None
None
Partial
Affected software
Redhat -> Enterprise linux desktop 
Redhat -> Enterprise linux eus 
Redhat -> Enterprise linux server 
Redhat -> Enterprise linux workstation 
Debian -> Debian linux 
Canonical -> Ubuntu linux 
Apache -> Spamassassin 

 References:
http://www.securityfocus.com/bid/105347
https://access.redhat.com/errata/RHSA-2018:2916
https://lists.apache.org/thread.html/7f6a16bc0fd0fd5e67c7fd95bd655069a2ac7d1f88e42d3c853e601c@%3Cannounce.apache.org%3E
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/

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