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Fencer Vulns
medium 5.0

CVE-2009-3720 json

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, allo…

published 2009-11-03 17 y ago modified 2026-07-20 3 mo ago also EUVD-2009-3693

cvss
5.0
version 2.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
27.9%
EPSS 27.9% chance of exploitation in 30 days, percentile 98%
public exploits
0
none known

Summary

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.

Patch / fix

  • apache http_server 2.0.64, 2.2.17
  • tla Debian 12 1.3.5+dfsg-15
  • gdcm Debian 14, Debian 13, Debian 12 2.0.14-2
  • poco Debian 14, Debian 13, Debian 12 1.3.6p1-1
  • tdom Debian 14, Debian 13, Debian 12 0.8.3~20080525-1
  • cmake Debian 14, Debian 13, Debian 12 2.6.0-6
  • coin3 Debian 14, Debian 13, Debian 12 4.0.0~CMake~6f54f1602475+ds1-1
  • expat Debian 14, Debian 13, Debian 12 2.0.1-5
  • xotcl Debian 14, Debian 13, Debian 12 1.6.5-1.2

debian advisories DEBIAN-CVE-2009-3720

  • python RHEL 5 2.4.3-44.el5
  • tkinter RHEL 5 2.4.3-44.el5
  • python-libs RHEL 5 2.4.3-44.el5
  • python-tools RHEL 5 2.4.3-44.el5
  • python RHEL 4 2.3.4-14.10.el4
  • tkinter RHEL 4 2.3.4-14.10.el4
  • python-tools RHEL 4 2.3.4-14.10.el4
  • PyXML RHEL 4 0.8.3-6.el4_8.2

red hat advisories RHSA-2011:0492RHSA-2011:0491RHSA-2010:0002RHSA-2009:1625RHSA-2009:1572

  • expat openSUSE Tumbleweed 2.2.0-3.1
  • apache2 openSUSE Tumbleweed 2.4.23-4.1
  • apr-util openSUSE Tumbleweed 1.5.4-4.4

opensuse advisories openSUSE-SU-2024:10077-1openSUSE-SU-2024:10268-1openSUSE-SU-2024:10568-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2009-3720 updated cvss 5.0

expat: buffer over-read and crash on XML with malformed UTF-8 sequences

  • Red Hat Desktop version 3 4Suite 0.11.1-15, expat 1.95.5-6.2
    fixed: vendor fix RHSA-2009:1572
  • Red Hat Enterprise Linux (v. 5 server) python 2.4.3-44.el5, tkinter 2.4.3-44.el5, PyXML 0.8.4-4.el5_4.2, expat 1.95.8-8.3.el5_4.2, python-libs 2.4.3-44.el5, python-tools 2.4.3-44.el5
    fixed: vendor fix RHSA-2009:1625
  • Red Hat Enterprise Linux AS version 3 4Suite 0.11.1-15, expat 1.95.5-6.2 Red Hat Enterprise Linux AS version 4 4Suite 1.0-3.el4_8.1, PyXML 0.8.3-6.el4_8.2, expat 1.95.7-4.el4_8.2, python 2.3.4-14.10.el4, tkinter 2.3.4-14.10.el4, python-tools 2.3.4-14.10.el4
    fixed: vendor fix RHSA-2009:1572
  • Red Hat Enterprise Linux Desktop (v. 5 client) python 2.4.3-44.el5, tkinter 2.4.3-44.el5, PyXML 0.8.4-4.el5_4.2, expat 1.95.8-8.3.el5_4.2, python-libs 2.4.3-44.el5, python-tools 2.4.3-44.el5
    fixed: vendor fix RHSA-2009:1625
  • Red Hat Enterprise Linux Desktop version 4 4Suite 1.0-3.el4_8.1, PyXML 0.8.3-6.el4_8.2, expat 1.95.7-4.el4_8.2, python 2.3.4-14.10.el4, tkinter 2.3.4-14.10.el4, python-tools 2.3.4-14.10.el4
    fixed: vendor fix RHSA-2009:1572
  • Red Hat Enterprise Linux Desktop Workstation (v. 5 client) python 2.4.3-44.el5, expat 1.95.8-8.3.el5_4.2
    fixed: vendor fix RHSA-2009:1625
  • Red Hat Enterprise Linux ES version 3 4Suite 0.11.1-15, expat 1.95.5-6.2 Red Hat Enterprise Linux ES version 4 4Suite 1.0-3.el4_8.1, PyXML 0.8.3-6.el4_8.2, expat 1.95.7-4.el4_8.2, python 2.3.4-14.10.el4, tkinter 2.3.4-14.10.el4, python-tools 2.3.4-14.10.el4 Red Hat Enterprise Linux WS version 3 4Suite 0.11.1-15, expat 1.95.5-6.2 Red Hat Enterprise Linux WS version 4 4Suite 1.0-3.el4_8.1, PyXML 0.8.3-6.el4_8.2, expat 1.95.7-4.el4_8.2, python 2.3.4-14.10.el4, tkinter 2.3.4-14.10.el4, python-tools 2.3.4-14.10.el4
    fixed: vendor fix RHSA-2009:1572
  • Red Hat JBoss Enterprise Application Platform 6.4
    fixed: vendor fix RHSA-2017:3239
show 2 more
  • Red Hat JBoss Web Server 1.0
    fixed: vendor fix RHSA-2011:0896
  • Red Hat Enterprise Linux 5 xmlrpc-c Red Hat Enterprise Linux 6 expat, PyXML, python, tkinter, python-libs, python-test, +2 more Red Hat Enterprise Linux 7 expat
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

27.92% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • expat.cvs.sourceforge.net http://expat.cvs.sourceforge.net/viewvc/expat/expat/lib/xmltok_impl.c?r1=1.13&r2=1.15&view=patch referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.