Vulnerability · CVE-2009-3720
CVE-2009-3720 is listed by inventory_critical.
Published Nov 3, 2009 · catalog updated Jul 20, 2026 · libexpat project
Last checked Nov 7, 2026. A connected source was read within the last 7 days.
Check this week
CVE-2009-3720 is not in CISA KEV. FIRST estimates a 27.92% chance of exploitation in the next 30 days. Check whether you run libexpat project.
Gaps on this record
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
Same product and reporting
- CVE-2026-115506 · High
- CVE-2026-41080 · Low
- CVE-2026-32778 · Medium
- CVE-2026-32777 · Medium
- CVE-2026-32776 · Medium
- Severity
- Medium5.0
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 27.92%
- Remediation
- Version ranges on file
- Affected products
- cpe apache/http server · cpe libexpat project/libexpat
CVE-2009-3720 is listed by inventory_critical.
Are you affected?
Enter the version you run. The result uses only the ranges stored on this record.
The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.
- cpe apache/http server< 2.0.64
- cpe apache/http server< 2.2.17
- cpe libexpat project/libexpat2.0.1
How to fix CVE-2009-3720
Upgrade
CVE-2009-3720 lists a fix boundary at 2.0.64. Compare the installed build with that boundary before you change production.
Version check
Affected < 2.0.64
Advisory
Open the cve_org record and follow its fix.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
CVE-2009-3720 is not in CISA KEV. FIRST estimates a 27.92% chance of exploitation in the next 30 days. Check whether you run libexpat project.
Which versions are affected?
Compare what you have installed with apache/http server < 2.0.64; apache/http server < 2.2.17; libexpat project/libexpat 2.0.1. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
No weakness class is stored. EPSS 27.92%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Nov 3, 2009 · Monitored products — critical
Detected
CVE-2009-3720 is listed by inventory_critical.
Jul 20, 2026 · Monitored products — critical
Updated
CVE-2009-3720 is listed by inventory_critical.
Sources
- CVE.orgVulnerability recordCVE-2009-3720
Official CVE identifier
cve.org - Monitored products — criticalVendor advisoryCVE-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.
nvd.nist.gov
References
- Exploit · expat.cvs.sourceforge.net
- Mailing List · expat.cvs.sourceforge.net
- Third Party Advisory · lists.fedoraproject.org
- Mailing List · lists.fedoraproject.org
- Third Party Advisory · lists.fedoraproject.org
- Third Party Advisory · lists.fedoraproject.org
- Third Party Advisory · lists.fedoraproject.org
- Third Party Advisory · lists.opensuse.org
Freshness
Last verified in this catalog Nov 7, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.
- CVE.orgNov 4, 2026
- Monitored products — criticalNov 4, 2026