Ghost in the shell: Investigating web shell attacks
To implant web shells, adversaries take advantage of security gaps in internet-facing web servers, typically vulnerabilities in web applications, for example CVE-2019-0604 or CVE-2019-16759.
CVE-2019-16759 KEVPublic exploit Critical · 9.8 EPSS 99.7%
vBulletin PHP Module Remote Code Execution Vulnerability
vBulletin · vBulletin
Summary
The vulnerability is in the PHP module of vBulletin, affecting versions 5.x through 5.5.4, where the widgetConfig[code] parameter in an ajax/render/widget_php request is not properly controlled, allowing code to be generated and executed. An attacker with network access can exploit it remotely without authentication or user interaction by sending a crafted request to that endpoint, achieving remote command execution on the server.
Official description · NVD
vBulletin 5.x through 5.5.4 allows remote command execution via the widgetConfig[code] parameter in an ajax/render/widget_php routestring request.
Priority scorePatchfirst’s 0 to 100 ranking. It adds points for CISA KEV listing, ransomware use, EPSS, threat reports, public exploit code and CVSS. Every CVE page shows the breakdown. Breakdown
73.7 / 100
- Exploited
- Yes, in CISA KEV
- Reports
- 1
- Tactics
- 2/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 15 days after disclosure. Public exploit code (Exploit-DB) was available 1 day before disclosure.
- Public exploit codeExploit-DB1 day before
- Disclosedday 0
- First seen exploitedVulnCheck KEV evidence+15 days
- Named in a threat reportmicrosoft.com+4 mo
- Added to CISA KEVEU database agrees+2 yrs
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
Patch historyEarlier and later CVEs in the same code, in date order. It shows when a fix was bypassed or incomplete and which version finally fixed it.
See the family treeA fix was bypassed or incomplete 2 times over 13 months.
Same bug familyLinked by evidence that a fix failed or the same code was patched again. Oldest first.
- This CVECVE-2019-16759vBulletin PHP Module Remote Code Execution24 Sep 2019KEV
incomplete fixHigh
Why these are linked: Link confidenceHow strong the evidence is that two CVEs are related. High: stated in the CVE text or linked in an advisory, or the same code was patched one release apart. Medium: the same code, or a version step plus a similar description. Low: similar description only.
- Stated in the CVE text
NOTE: this issue exists because of an incomplete fix for CVE-2019-16759.
- Stated in the CVE text
- same family
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
2 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order, 2 cited passages 11Initial AccessTA0001
Exploit Public-Facing Application T1190 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
MITRE CTID mapping of the CVE · uncategorised
ExecutionTA0002
Command and Scripting Interpreter T1059 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · primary impact
Injected code executes commands on the server
allows remote command execution via the widgetConfig[code] parameter
Detection
0 rules for this CVE · 244 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2019-16759 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Command and Scripting InterpreterT105995 general rules
- HackTool - Sliver C2 Implant Activity Patterncriticaltest
- Lazarus Group Activitycriticaltest
- REvil Kaseya Incident Malware Patternscriticaltest
- Turla Group Lateral Movementcriticaltest
- Windows Defender AMSI Trigger Detectedhighstable
- Windows Defender Threat Detectedhighstable
- Abusable DLL Potential Sideloading From Suspicious Locationhightest
- Add Insecure Download Source To Wingethightest
Exploit Public-Facing ApplicationT1190149 general rules
- Arcadyan Router Exploitationscriticaltest
- Citrix ADS Exploitation CVE-2020-8193 CVE-2020-8195criticaltest
- Citrix Netscaler Attack CVE-2019-19781criticaltest
- Confluence Exploitation CVE-2019-3398criticaltest
- CVE-2010-5278 Exploitation Attemptcriticaltest
- CVE-2020-0688 Exchange Exploitation via Web Logcriticaltest
- CVE-2020-10148 SolarWinds Orion API Auth Bypasscriticaltest
- CVE-2020-5902 F5 BIG-IP Exploitation Attemptcriticaltest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Named in 1 threat report1 reportMicrosoftFeb 2020
Reports are matched by finding the exact id CVE-2019-16759 in their text; nobody has reviewed the match. One passage is shown per report, at most 320 characters, linked to the original.
Also mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- Actively_Exploited_Kev | Oct 22, 202621 Oct 2026
- 44 more on OTX