CVE-2009-3720

CVE-2009-3720 is a medium-severity vulnerability in Libexpat Project Libexpat with a CVSS 2.0 base score of 5.0. Its EPSS exploit-prediction score of 28% places it in the 98th percentile, indicating an elevated likelihood of exploitation.

Key facts

Description

The updatePosition function in lib/xmltok_impl.c in libexpat in Expat 2.0.1, as used in Python, PyXML, w3c-libwww, and other software, allows context-dependent attackers to cause a denial of service (application crash) via an XML document with crafted UTF-8 sequences that trigger a buffer over-read, a different vulnerability than CVE-2009-2625.

Frequently asked questions

What is CVE-2009-3720?
The updatePosition function in lib/xmltok_impl.c in libexpat in Expat 2.0.1, as used in Python, PyXML, w3c-libwww, and other software, allows context-dependent attackers to cause a denial of service (application crash) via an XML document with crafted UTF-8 sequences that trigger a buffer over-read, a different vulnerability than CVE-2009-2625.
How severe is CVE-2009-3720?
CVE-2009-3720 has a CVSS 2.0 base score of 5.0, rated medium severity.
Is CVE-2009-3720 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 28% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2009-3720?
CVE-2009-3720 primarily affects Libexpat Project Libexpat. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2009-3720?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2009-3720 published?
CVE-2009-3720 was published on 2009-11-03 and last updated on 2026-06-16.

References

Affected products (2)

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Threat intelligence

Threat-intel indicators referencing this CVE: