Libexpat Project CVEs & Vulnerabilities

libexpat before 2.8.2 does not consider XML_TOK_DATA_CHARS in doCdataSection and thus lacks handler call depth tracking for various calls from within handlers in cases of a policy violation. Thus, a use-after-free can occur. NOTE: this issue exists because of an incomplete fix for CVE-2026-50219.

xmlwf in libexpat before 2.8.2 has an integer overflow in endDoctypeDecl via NOTATION declarations.

xmlwf in libexpat before 2.8.2 has an integer overflow in resolveSystemId.

xmlwf in libexpat before 2.8.2 has an integer overflow for the output filename when -d outputDir is used.

libexpat before 2.8.2 has an integer overflow in copyString.

libexpat before 2.8.2 has an integer overflow in doProlog that is related to storeEntityValue and entity textLen.

libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was present in XML_Parse.

libexpat before 2.8.2 has an integer overflow in getAttributeId.

libexpat before 2.8.2 has an integer overflow in addBinding.

libexpat before 2.8.2 has an integer overflow in storeAtts.

In libexpat before 2.8.2, there is a heap-based buffer overflow in doProlog in xmlparse.c because scaffold backing array reallocation is mishandled when there is data-structure sharing across parsers.

libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).

libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_GetBuffer, XML_Parse, XML_ParseBuffer, XML_ParserFree, or XML_ParserReset from within handlers in cases of a policy violation. Thus, a use-after-free can occur,

`xml.parsers.expat` and `xml.etree.ElementTree` use insufficient entropy for Expat hash-flooding protection, which allows a crafted XML document to trigger hash flooding.\r\n\r\nFully mitigating this vulnerability requires both updating libexpat to 2.8.0 or later and applying this patch.

In libexpat before 2.8.1, the computational complexity of attribute name collision checks allows a denial of service via moderately sized crafted XML input.

libexpat before 2.7.5 allows a NULL pointer dereference in the function setContext on retry after an earlier ouf-of-memory condition.

libexpat before 2.7.5 allows an infinite loop while parsing DTD content.

libexpat before 2.7.5 allows a NULL pointer dereference with empty external parameter entity content.