Last updated 24 September 2026

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.

Expat Denial of Service via storeAtts() Quadratic Complexity

Last updated 21 September 2026

Last updated 24 September 2026

Last updated 24 September 2026

Last updated 24 September 2026

Last updated 21 September 2026

Last updated 24 September 2026

Last updated 24 September 2026

Last updated 21 September 2026

Last updated 21 September 2026

Last updated 21 September 2026

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 XMLResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation).

Last updated 21 September 2026

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.

Last updated 21 September 2026

Last updated 21 September 2026

Last updated 21 September 2026

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

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.

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

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.

Accessibility. A privacy issue was addressed by removing sensitive data.

An issue was discovered in libexpat before 2.6.4. There is a crash within the XMLResumeParser function because XMLStopParser can stop/suspend an unstarted parser.

An issue was discovered in libexpat before 2.6.3. dtdCopy in xmlparse.c can have an integer overflow for nDefaultAtts on 32-bit platforms (where UINTMAX equals SIZEMAX).

Accounts. A logic issue was addressed with improved file handling.

An issue was discovered in libexpat before 2.6.3. nextScaffoldPart in xmlparse.c can have an integer overflow for mgroupSize on 32-bit platforms (where UINTMAX equals SIZEMAX).

libexpat could allow a remote attacker to obtain sensitive information, caused by improper handling of XML external entity (XXE) declarations by the XMLExternalEntityParserCreate function. By using a specially crafted XML content, a remote attacker could exploit this vulnerability to obtain sensitive information, and use this information to launch further attacks against the affected system.