CVE-2021-45958: 
Python vulnerability analysis and mitigation

UltraJSON (aka ujson) through version 5.1.0 contains a stack-based buffer overflow vulnerability in the Buffer_AppendIndentUnchecked function when called from encode. The vulnerability was discovered in late 2021 and assigned CVE-2021-45958. The issue affects all versions of ujson up to and including 5.1.0 (NVD, OSS-Fuzz).

The vulnerability occurs in the Buffer_AppendIndentUnchecked function when handling indentation during JSON encoding. The buffer overflow can be triggered by using a large amount of indentation in the JSON encoding process. The issue has been assigned a CVSS v3.1 Base Score of 5.5 (Medium) with vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H (NVD).

When exploited, this vulnerability can lead to a denial of service condition through program crashes. The buffer overflow could potentially corrupt memory, though no confidentiality or integrity impacts have been reported (USN-6629-1).

The vulnerability was fixed in version 5.2.0 of ujson. Users are recommended to upgrade to this version or later. The fix includes proper buffer overflow checks and improved memory handling (Fedora Update).