Threats affecting pkg:github/libexpat/libexpat

A signed integer overflow vulnerability exists in libexpat versions through 2.9.0 in the storeAtts() function within lib/xmlparse.c. This flaw allows attackers to cause out-of-bounds writes by supplying XML documents with an excessively large number of attributes, potentially leading to application crashes or heap memory corruption.

A NULL pointer dereference vulnerability exists in libexpat through version 2.9.0 within the externalEntityInitProcessor2() function. This flaw mishandles the XML_TOK_NONE token from empty input, allowing attackers who control stream chunking to cause a crash by forcing an empty non-final first parse on an external entity subparser.

libexpat versions 2.7.2 through 2.8.5 contain an integer overflow vulnerability in the expat_realloc() function on 32-bit platforms. This vulnerability can cause heap buffer overflow, memory corruption, or denial of service when processing malicious XML data. The CVSS score is 5.9, indicating medium severity.

CVE-2026-76957 is a use-after-free vulnerability in libexpat that affects versions prior to 2.8.4. The issue occurs due to missing handler call depth tracking when using custom encoding callbacks, which can cause premature freeing of memory and subsequent access. The vulnerability has a medium severity rating with a CVSS score of 4.9.

CVE-2026-76956 is a vulnerability in libexpat versions 2.8.2 and 2.8.3 prior to 2.8.4 where the return code of the getentropy function is misinterpreted. This leads to insufficient entropy being used, making the software vulnerable to hash flooding attacks that can cause denial of service through crafted XML content.

libexpat before 2.8.3 has an out-of-bounds read and resultant infinite loop because low surrogates are treated the same as high surrogates during Unicode processing in the *_toUtf16 functions.

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.

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

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 getAttributeId.

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,

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 2.8.0 uses insufficient entropy, and thus hash flooding can occur via a crafted XML document.

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.