Vulnerability details

b2evolution CMS versions 6.7.8 through 7.2.5 contain an incomplete fix for CVE-2016-8901 where the serialized-array object check in param_check_serialized_array() fails to reject payloads with negative integer array keys. Unauthenticated attackers can submit crafted serialized PHP objects via POST requests to htsrv/call_plugin.php that bypass validation and reach unserialize(), instantiating arbitrary PHP objects with attacker-chosen properties that may enable code execution if suitable POP gadget chains exist.

• https://gist.github.com/axg11/3e29501c33f6e1e05ac2a00107afd64e technical-description
• https://github.com/b2evolution/b2evolution/blob/7.2.5/inc/_core/_param.funcs.php#L2860 technical-description
• https://github.com/b2evolution/b2evolution/blob/7.2.5/htsrv/call_plugin.php#L49 technical-description
• https://github.com/b2evolution/b2evolution/commit/25c21cf9cc4261324001f9039509710b37ee2c4d patch
• https://github.com/b2evolution/b2evolution/commit/999b5ad1d59760d7e450ceb541f55432fc74cd27 patch
• https://github.com/b2evolution/b2evolution/commit/335abf09bcea61717bd00bc1e3889f8100ebd1bb technical-descriptionpatch
• https://b2evolution.net/news/2022/03/26/2022-update-eol vendor-advisory
• https://github.com/b2evolution/b2evolution product
• https://www.vulncheck.com/advisories/b2evolution-cms-6.7.8-through-7.2.5-object-injection-via-negative-integer-array-key third-party-advisory