Libexpat Project Libexpat CVEs.

libexpat in Expat before 2.7.2 allows attackers to trigger large dynamic memory allocations via a small document that is submitted for parsing.

Libexpat Project Libexpat

Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.

Denial of service Library Libexpat Project Libexpat

libexpat 2.7.2 through 2.9.0 contains a denial of service vulnerability because XML_ParserReset zeroes the direct byte count but never offsets tracked heap allocations. Attackers can submit a large XML document so later documents on the same reset parser fail with XML_ERROR_NO_MEMORY until it is recreated.

Denial of service Library Libexpat Project Libexpat

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 Project Libexpat

libexpat through 2.9.0 contains a denial of service vulnerability because billion laughs protection in accountingDiffTolerated() in xmlparse.c detects entity amplification too late. Attackers can supply a moderately sized XML document with a large DTD and nested entity expansions to consume tens of seconds of CPU per parse.

Denial of service Library Libexpat Project Libexpat

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.

Memory safety Libexpat Project Libexpat

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

Libexpat Project Libexpat

libexpat through 2.9.0 contains a signed integer overflow vulnerability in storeAtts() in lib/xmlparse.c that allows attackers to trigger out-of-bounds writes via oversized attribute counts. Attackers can supply a multi-gigabyte document with a start tag carrying over 2^30 attributes to overflow attIndex and nPrefixes, crashing applications or corrupting heap memory.

Memory safety Library Libexpat Project Libexpat

In libexpat 2.8.2 and 2.8.3 before 2.8.4, misinterpretation of getentropy's return code leads to insufficient entropy, which results in being vulnerable to hash flooding attacks, causing a denial of service via crafted XML content.

Denial of service Libexpat Project Libexpat

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

Libexpat Project Libexpat

In libexpat through 2.7.3, a crafted file with an approximate size of 2 MiB can lead to dozens of seconds of processing time.

Libexpat Project Libexpat

In libexpat before 2.7.4, the doContent function does not properly determine the buffer size bufSize because there is no integer overflow check for tag buffer reallocation.

Libexpat Project Libexpat

In libexpat before 2.7.4, XML_ExternalEntityParserCreate does not copy unknown encoding handler user data.

Libexpat Project Libexpat

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,

Libexpat Project Libexpat

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.

Libexpat Project Libexpat

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

Libexpat Project Libexpat

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 Project Libexpat

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

Libexpat Project Libexpat

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

Libexpat Project Libexpat

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

Libexpat Project Libexpat

libexpat before 2.8.2 has an integer overflow in storeAtts.

Libexpat Project Libexpat

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 Project Libexpat

libexpat before 2.8.2 has an integer overflow in addBinding.

Libexpat Project Libexpat

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

Libexpat Project Libexpat

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

Libexpat Project Libexpat

libexpat before 2.8.2 has an integer overflow in getAttributeId.

Libexpat Project Libexpat

libexpat before 2.8.2 has an integer overflow in copyString.

Libexpat Project Libexpat

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

Libexpat Project Libexpat

libexpat before 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, a use-after-free can occur. NOTE: this is similar to CVE-2026-50219, CVE-2026-56131 and CVE-2026-56412.

Memory safety Libexpat Project Libexpat