CVE-2020-17496
vBulletin PHP Module Remote Code Execution Vulnerability
Description
CVE-2020-17496 is a critical injection vulnerability affecting vBulletin versions 5.5.4 through 5.6.2. The vulnerability allows remote command execution via crafted subWidgets data in an ajax/render/widget_tabbedcontainer_tab_panel request. This vulnerability exists because of an incomplete fix for CVE-2019-16759 and enables unauthenticated attackers to execute arbitrary commands on the server. CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. With an EPSS score of 94.18% (99.92nd percentile), this vBulletin vulnerability has a near-certain probability of exploitation.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorCWEs
Affected Products
| Vendor | Product | Version |
|---|---|---|
| vbulletin | vbulletin | >= 5.5.4, <= 5.6.2 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://blog.exploitee.rs/2020/exploiting-vbulletin-a-tale-of-patch-fail/(Exploit, Third Party Advisory)
- https://cwe.mitre.org/data/definitions/78.html(Technical Description)
- https://forum.vbulletin.com/forum/vbulletin-announcements/vbulletin-announcements_aa/4445227-vbulletin-5-6-0-5-6-1-5-6-2-security-patch(Patch, Vendor Advisory)
- https://seclists.org/fulldisclosure/2020/Aug/5(Exploit, Mailing List, Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-17496(US Government Resource)
Weakness Type
CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component (‘Injection’)
Injection vulnerabilities occur when software constructs output using externally-influenced input without properly neutralizing special elements that could be interpreted as control directives. In CVE-2020-17496, the vBulletin widget rendering subsystem fails to properly neutralize crafted subWidgets data in the ajax/render/widget_tabbedcontainer_tab_panel endpoint, allowing attackers to inject and execute arbitrary commands on the underlying server.
Learn more: CWE-74 — Improper Neutralization of Special Elements in Output Used by a Downstream Component
Impact Analysis
CVE-2020-17496 carries a CVSS 3.1 score of 9.8 (CRITICAL), the highest practical severity rating. The vulnerability is remotely exploitable over the network with low attack complexity, requires no authentication, and needs no user interaction. Successful exploitation completely compromises the confidentiality, integrity, and availability of the affected vBulletin server, enabling attackers to execute arbitrary commands with the web server’s privileges. The EPSS score of 94.18% places this vulnerability in the 99.92nd percentile, indicating near-certain exploitation activity. This is particularly dangerous because it bypasses the patch for CVE-2019-16759, meaning organizations that believed they were protected may still be vulnerable.
Exploit Maturity
Public exploit code is available for CVE-2020-17496 via exploitee.rs detailing the incomplete patch bypass, as well as through Full Disclosure mailing list. CISA has confirmed active exploitation in the wild through its KEV catalog. The EPSS score of 94.18% (99.92nd percentile) indicates near-certain exploitation activity. This vulnerability is directly related to CVE-2019-16759 and demonstrates a patch bypass scenario: the original fix blocked the widgetConfig[code] parameter but failed to address the subWidgets data vector in the widget_tabbedcontainer_tab_panel route, allowing attackers to achieve the same remote code execution through an alternative path.
Remediation
- Apply vendor patches immediately as mandated by CISA KEV: Apply updates per vendor instructions. Install the vBulletin security patch for versions 5.6.0, 5.6.1, and 5.6.2 as published by the vendor.
- Verify that all vBulletin instances running versions 5.5.4 through 5.6.2 have received both the CVE-2019-16759 and CVE-2020-17496 patches, as the former had an incomplete fix.
- Restrict access to the ajax/render/widget_tabbedcontainer_tab_panel route using web server configuration or WAF rules to block crafted subWidgets payloads.
- Deploy a web application firewall (WAF) with rules specifically targeting injection patterns in vBulletin widget rendering endpoints.
- Review server access logs and web application logs for suspicious requests to widget_tabbedcontainer_tab_panel endpoints, and conduct incident response if exploitation indicators are found.
Technical Details
CVE-2020-17496 is an injection vulnerability in the vBulletin widget rendering subsystem that exists due to an incomplete fix for CVE-2019-16759. While the original patch restricted the widgetConfig[code] parameter in the widget_php route, attackers discovered that crafted subWidgets data sent to the ajax/render/widget_tabbedcontainer_tab_panel endpoint could achieve the same arbitrary command execution. The vulnerability maps to CWE-74, as the application fails to properly neutralize special elements in user-supplied input before using it in a downstream component. The CVSS vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H confirms that the attack is network-based, trivially exploitable without authentication or user interaction, and results in complete compromise of confidentiality, integrity, and availability.
Frequently Asked Questions
Is CVE-2020-17496 being actively exploited?
Yes. CVE-2020-17496 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation. The EPSS score of 94.18% (99.92nd percentile) indicates near-certain exploitation activity. Public exploit code and detailed analysis of the incomplete patch bypass are readily available.
What products are affected by CVE-2020-17496?
CVE-2020-17496 affects vBulletin versions 5.5.4 through 5.6.2. This vulnerability specifically targets the widget_tabbedcontainer_tab_panel rendering endpoint and exists because of an incomplete fix for CVE-2019-16759.
How do I fix CVE-2020-17496?
Apply updates per vendor instructions by installing the vBulletin security patch for versions 5.6.0, 5.6.1, and 5.6.2. Ensure both CVE-2019-16759 and CVE-2020-17496 patches are applied. As an interim measure, deploy WAF rules to block crafted subWidgets payloads targeting the widget_tabbedcontainer_tab_panel route.
How severe is CVE-2020-17496?
CVE-2020-17496 has a CVSS 3.1 score of 9.8 (CRITICAL). This is a maximum-severity vulnerability that enables unauthenticated remote command execution on vBulletin servers and bypasses the original patch for CVE-2019-16759.
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