libexpat in Expat before 2.7.2 allows attackers to trigger large dynamic memory allocations via a small document that is submitted for parsing.
https://issues.oss-fuzz.com/issues/439133977
https://github.com/libexpat/libexpat/pull/1034
https://github.com/libexpat/libexpat/issues/1018
https://github.com/libexpat/libexpat/blob/R_2_7_2/expat/Changes