Published : May 16, 2026, 4:16 p.m. | 8 hours, 30 minutes ago
Description :TextPattern CMS 4.9.0-dev contains a remote code execution vulnerability that allows authenticated attackers to upload arbitrary PHP files by exploiting the plugin upload functionality. Attackers can authenticate, retrieve a CSRF token from the plugin event page, and upload malicious PHP files to the textpattern/tmp/ directory for code execution.
Severity: 8.8 | HIGH
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🤖 AI-Generated Patch Solution
Google Gemini (gemini-2.5-flash) • CVE: CVE-2021-47976
N/A
Immediately identify all Linux systems running kernels that utilize the netfilter nf_tables subsystem. This vulnerability affects systems with specific older kernel versions.
Restrict administrative access to identified systems, particularly limiting non-root users from obtaining CAP_NET_ADMIN capabilities. This capability is required to trigger the vulnerability.
If immediate patching is not feasible for critical systems, consider temporary isolation from less trusted networks to reduce the attack surface.
Review system logs (dmesg, /var/log/kern.log, journalctl -k) for any recent kernel panics, crashes, or unusual error messages, especially those mentioning "use-after-free" or "nf_tables" which could indicate an attempted exploitation or system instability.
2. PATCH AND UPDATE INFORMATION
The vulnerability CVE-2021-47976, a use-after-free flaw in the Linux kernel's netfilter nf_tables component, was addressed in the following stable kernel releases:
Linux kernel 5.10.79
Linux kernel 5.15.5
Linux kernel 5.16-rc3 (and subsequent stable releases in the 5.16.x series)
To remediate, update your Linux kernel packages to the latest stable version available from your distribution vendor that includes these fixes or newer.
For Debian/Ubuntu-based systems: Execute 'sudo apt update && sudo apt upgrade linux-image-generic'
For Red Hat/CentOS/Fedora-based systems: Execute 'sudo yum update kernel' or 'sudo dnf update kernel'
A system reboot is required after updating the kernel packages to ensure the new, patched kernel is loaded and active.
Verify the active kernel version post-reboot using the command 'uname -r' and confirm it is a version equal to or newer than the fixed versions mentioned above.
3. MITIGATION STRATEGIES
Restrict CAP_NET_ADMIN capability: Minimize the number of users or processes that have the CAP_NET_ADMIN capability. This capability allows manipulation of network configurations, including netfilter rules, and is necessary for exploiting this vulnerability.
Utilize Linux Security Modules (LSMs): Implement and enforce strict policies using SELinux or AppArmor. Custom policies can be crafted to limit the scope of actions for processes, even those with CAP_NET_ADMIN, potentially preventing the specific nf_tables operations that trigger the use-after-free.
Network Segmentation: Isolate critical servers and services into separate network segments. This limits an attacker's lateral movement and reduces the potential impact if a system is compromised.
Monitor Netfilter Rule Changes: Implement logging and alerting for any significant or unusual modifications to nf_tables rulesets, especially if initiated by non-privileged accounts or at unusual times.
Kernel Module Disabling (with caution): If nf_tables functionality is not actively used on a system, consider temporarily blacklisting or disabling the 'nf_tables' kernel module. However, this may