A vulnerability was discovered in the PyYAML library in versions before 5.4, where it is susceptible to arbitrary code execution when it processes untrusted YAML files through the full_load method or with the FullLoader loader. Applications that use the library to process untrusted input may be vulnerable to this flaw. This flaw allows an attacker to execute arbitrary code on the system by abusing the python/object/new constructor. This flaw is due to an incomplete fix for CVE-2020-1747.

A vulnerability was discovered in the PyYAML library in versions before 5.3.1, where it is susceptible to arbitrary code execution when it processes untrusted YAML files through the full_load method or with the FullLoader loader. Applications that use the library to process untrusted input may be vulnerable to this flaw. An attacker could use this flaw to execute arbitrary code on the system by abusing the python/object/new constructor.

PyYAML 5.1 through 5.1.2 has insufficient restrictions on the load and load_all functions because of a class deserialization issue, e.g., Popen is a class in the subprocess module. NOTE: this issue exists because of an incomplete fix for CVE-2017-18342.

In PyYAML before 5.1, the yaml.load() API could execute arbitrary code if used with untrusted data. The load() function has been deprecated in version 5.1 and the 'UnsafeLoader' has been introduced for backward compatibility with the function.

scanner.c in LibYAML 0.1.5 and 0.1.6, as used in the YAML-LibYAML (aka YAML-XS) module for Perl, allows context-dependent attackers to cause a denial of service (assertion failure and crash) via vectors involving line-wrapping.

Heap-based buffer overflow in the yaml_parser_scan_uri_escapes function in LibYAML before 0.1.6 allows context-dependent attackers to execute arbitrary code via a long sequence of percent-encoded characters in a URI in a YAML file.

The yaml_parser_scan_tag_uri function in scanner.c in LibYAML before 0.1.5 performs an incorrect cast, which allows remote attackers to cause a denial of service (application crash) and possibly execute arbitrary code via crafted tags in a YAML document, which triggers a heap-based buffer overflow.