CVE-2017-15705 Denial of service in Apache SpamAssassin

Medium 5.3 Published 17 Sep 2018 Updated 16 Sep 2024

Crafted emails with unclosed tags cause excessive scan times in Apache SpamAssassin, leading to denial of service.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2017-15705?

CVE-2017-15705 is a medium-severity denial of service vulnerability in Canonical Ubuntu Linux, published on 17 Sep 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Weakness: CWE-20

Which versions are affected by CVE-2017-15705?

It affects 7 products.

Products include Apache Spamassassin, Canonical Ubuntu Linux, Debian Debian Linux, Redhat Enterprise Linux Desktop, Redhat Enterprise Linux Eus, Redhat Enterprise Linux Server and 1 more.

How do I fix CVE-2017-15705?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2017-15705 being exploited?

There is no known exploitation of CVE-2017-15705 in the wild and no public exploit code.

All Canonical Ubuntu Linux vulnerabilities

Sources

Also known as ALPINE-CVE-2017-15705, DEBIAN-CVE-2017-15705, GHSA-m63q-qrvc-wwrm, UBUNTU-CVE-2017-15705.