Description
libexpat through 2.9.0 contains a NULL pointer dereference vulnerability in externalEntityInitProcessor2() in lib/xmlparse.c that mishandles the XML_TOK_NONE token from empty input. Attackers who control stream chunking can force an empty non-final first parse on an external entity subparser, causing a later parse to crash the application.
Affected products
libexpat_project: libexpat
References5
- www.vulncheck.com/advisories/libexpat-through-2.9.0-null-pointe… PatchVendor Advisory
- github.com/libexpat/libexpat/commit/7b0d50e4b1d16fafd5587626070… Patch
- github.com/libexpat/libexpat/pull/1444 Patch
- github.com/libexpat/libexpat Product
- github.com/libexpat/libexpat/blob/a76b1174c1ea52abb639a4c69d52b… Product
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 4.0
-
8.2
HIGH
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 37 · as of 2 November 2026
- CWE
- CWE-476
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