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CVE-2017-15705

UnknownEPSS 7.88%

Last modified

CVE-2017-15705 is a vulnerability of currently unknown severity. 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. EPSS estimates a 7.88% chance of exploitation in the next 30 days.

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.

Metrics

EPSS Probability
7.88%

94.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
ApacheSpamassassin< 3.4.2
CanonicalUbuntu Linux12.04
CanonicalUbuntu Linux14.04
CanonicalUbuntu Linux16.04
CanonicalUbuntu Linux18.04
DebianDebian Linux8.0
RedhatEnterprise Linux Desktop7.0
RedhatEnterprise Linux Eus7.5
RedhatEnterprise Linux Server7.0
RedhatEnterprise Linux Workstation7.0

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2017-15705?
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.
How severe is CVE-2017-15705?
Severity scoring for CVE-2017-15705 is pending analysis. The EPSS model estimates a 7.88% probability of exploitation in the next 30 days.
How do I fix CVE-2017-15705?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST