CVE-2009-3720
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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…
rank 25 = 7 + 13 + 0 + 5 + 0
rank@v1 · scheduled
Someone is already using it
CISA KEV catalog · public proof-of-concept · FIRST EPSS
EPSS 0.27924 · without this subject the record ranks 18
What it costs you if it fires
NVD CVSS base score, then the CNA's own
CVSS 5.0, from NVD · without this subject the record ranks 12
It is getting worse, not staying still
FIRST EPSS series, rescorings and bad loads removed
no persisting rise in 365 days · without this subject the record ranks 25
How much of the world it touches
NVD CPE configurations
3 products in the CPE ranges · without this subject the record ranks 20
Someone else already set the date
CISA KEV remediation due date
no CISA due date · without this subject the record ranks 25
$399,000 = $4.99M incident cost x 0.28625080150224425 exposure x 0.27924 likelihood
udv@v1 · unaudited · wrong for you until you say what you run
$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.
Hindsight · the state
Foresight · where to check next
No weakness class or product neighbourhood is held for this record, so this index cannot name anywhere to check next. That is an absence in the record, not a finding about the software.
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Harm, if it fires from the vector and the weakness
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CISA KEV & Federal Remediation Deadline from the record and CISA
The fix, and how long it's been waiting.
Exploit Status & Known PoCs a ladder, not a score
Current rung: Nothing observed in held sources.
- RUNG 1Nothing observed in held sources
- RUNG 2Proof-of-concept published
- RUNG 3Exploited in the wild · CISA KEV listed
- RUNG 4Ransomware campaign use known
A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.
What it is stated by the CNA
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. receipt
NVD's analysis a second authority
- severity
- 5 AV:N/AC:L/Au:N/C:N/I:N/A:P
- affected versions
- libexpat project libexpat 2.0.1; apache http server >= 2.0.35 < 2.0.64; apache http server >= 2.2.0 < 2.2.17
check it yourself slackware.com svn.python.org mandriva.com lists.fedoraproject.org redhat.com redhat.com +14 morereceipt
Movement the material steps
This score more than doubled inside 72 hours. Both observations are in the full history below.
Show all 62 observations
62 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt
The full biography
Exploit probability more than doubled between 2025-03-27 and 2025-03-29 (0.00762 → 0.01585) and the record had been public for 16 years, 7 months when this index was last written.
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What usually comes next
Everything above needs no account. What is below is work: assembling it, scoping it to your estate, watching it, and handing it to someone else.