Live Exposure Defense: From CVE to Confirmed Exposure in 12 Hours – See more

Back
New CVE Detected

CVE-2026-76834 – Unauthenticated PHP Object Injection (RCE) – b2evolution CMS 6.7.8–7.2.5

Be the first to know when new zero-days emerge:

Subscribe to Email Alerts
Subscribe to RSS Feed

Summary

CVE-2026-76834 is a critical deserialization vulnerability (CWE-502) in b2evolution CMS affecting versions 6.7.8 through 7.2.5. The flaw is an incomplete fix for the older CVE-2016-8901 issue: the input-validation routine param_check_serialized_array() fails to reject serialized array payloads that use negative integer array keys, allowing an unauthenticated attacker to smuggle crafted serialized data into PHP’s unserialize() function. The CVE carries a CVSS score of 9.2 (Critical).

Technical details

  • Root cause: The validation check in param_check_serialized_array() (in b2evolution’s parameter-handling code) is intended to reject any array key that is not a non-negative integer, but its logic incorrectly allows negative integer keys (e.g. -1) to pass through unrejected.
  • Trigger conditions: An attacker submits a specially crafted serialized PHP payload — such as a:-1:{i:-1;O:8:"stdClass":0:{}} — using a negative array key to bypass the sanitization check.
  • Attack vector: The malicious payload is delivered via an unauthenticated POST request to htsrv/call_plugin.php, which passes attacker-controlled data through to PHP’s unserialize().
  • Impact: Successful exploitation results in PHP Object Injection, allowing instantiation of arbitrary PHP objects with attacker-chosen properties. Depending on the presence of exploitable "POP gadget chains" elsewhere in the application or its plugins, this can escalate to remote code execution, arbitrary file read/write, or SQL injection. No authentication is required to exploit the flaw.

Affected software

  • b2evolution CMS versions 6.7.8 through 7.2.5 (inclusive)

Severity

  • CVSS 4.0 Base Score: 9.2 (Critical)
  • Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Mitigation and recommended actions

  • Immediate: As of this writing, no official patched release beyond 7.2.5 has been published by the b2evolution project, which has been largely unmaintained since its last stable release. Organizations should monitor the b2evolution GitHub repository for an official fix and apply it as soon as it becomes available.
  • If no patch is available:
    • Restrict or block external access to htsrv/call_plugin.php at the web server, reverse proxy, or WAF layer if the endpoint is not required for legitimate use.
    • Deploy WAF/IPS rules to detect and block serialized PHP payloads (e.g. patterns containing O: object markers or negative array-length indicators like a:-) submitted to CMS endpoints.
    • Given the product’s end-of-life status, evaluate migrating affected sites to an actively maintained CMS platform.
    • Monitor logs for anomalous POST requests to plugin-handling endpoints and for unexpected PHP errors indicative of failed deserialization attempts.

References

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report

How IONIX’s External Exposure Management Platform Detects and Validates
Zero-Days to Shrink MTTR

1

Map your entire attack surface (continously)

IONIX uses multi-factor discovery methods, including DNS analysis, certificate mapping, metadata inspection, and more, to automatically map every internet-facing asset across your environment. This includes cloud instances, third-party platforms, shadow IT, and even forgotten infrastructure that traditional tools miss.

2

Monitor for new CVEs

Dozens of threat intel feeds using agentic technology are continuously analyzed to detect the appearance of proof-of-concept code, exploit kits, and indicators of active targeting. IONIX goes further by applying AI to proactively evaluate whether emerging vulnerabilities are likely to be exploited, even before PoCs go public.

3

Identify Potential External Exposures

Not all CVEs matter. IONIX filters vulnerabilities by asking attacker-centric questions: Can it be reached from the internet? Does it require authentication? Is it being exploited in the wild? This dramatically reduces noise and focuses teams on threats that can actually be weaponized.

4

Create Safe, Scalable Exploit Validations

IONIX transforms real-world PoCs into safe, non-intrusive test payloads that can be run in production environments without disruption. These simulations are precisely targeted to the systems that are vulnerable, ensuring rapid validation without unnecessary load.

5

Execute Exploit Validations

By combining context about software stack, versioning, exposure status, and reachability, IONIX ensures that only the right payloads are executed against the right assets, maximizing efficiency and minimizing risk.

6

Drive Fast and Actionable Remediation

Results are routed through integrations with ticketing, SOAR, and SIEM tools. Issues are written in plain language, bundled into remediation clusters, and prioritized based on asset criticality, exploitability, and blast radius. This shortens mean time to remediation (MTTR) and empowers teams to act with confidence.

Are you exposed?

Get a free report of your organization’s exposure to this CVE and threat

  • Mapping of all Assets with this Technology
  • Identification of potentially exposed assets to this CVE
  • Confirmation of verified exploitable assets
Get Exposure Report
Close

Subscribe to Threat Center RSS

Copy/paste the link below into your preferred RSS reader or follow these instructions to subscribe to Slack alerts.

Open RSS feedSlack setup instructions

Close

Get Real-Time CVE Alerts to Your Email

Be the first to know when new zero-days emerge