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 fullload 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 fullload 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.

A vulnerability was discovered in the PyYAML library, where it is susceptible to arbitrary code execution when it processes untrusted YAML files through the fullload 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/apply constructor.

In PyYAML before 4.1, the yaml.load() API could execute arbitrary code. In other words, yaml.safeload is not used.

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 yamlparserscanuriescapes 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.

A heap-based buffer overflow flaw was found in the way libyaml parsed YAML tags. A remote attacker could provide a specially-crafted YAML document that, when parsed by an application using libyaml, would cause the application to crash or, potentially, execute arbitrary code with the privileges of the user running the application.

Acknowledgements:

This issue was discovered by Florian Weimer of the Red Hat Product Security Team.