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VulnerabilitiesOct 15, 2026

Hackers exploit Collabora RCE flaw to backdoor Nextcloud servers

Hackers exploit Collabora RCE flaw to backdoor Nextcloud servers via CVE-2026-110447.

Threat actors are actively exploiting a critical command execution vulnerability (CVE-2026-110447) in the Collabora Online app for Nextcloud, allowing them to backdoor servers. Attacks began in mid-September, with attackers planting webshells to search for sensitive data. The vulnerability impacts specific versions of the built-in CODE server app and requires the server to be stopped for exploitation, with no authentication needed.

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The lesson from this incident

Full lesson

Attackers are actively exploiting CVE-2026-110447, a critical unauthenticated remote code execution vulnerability in the Collabora Online (CODE) app bundled with Nextcloud, to plant webshells and exfiltrate sensitive data. The flaw requires no authentication, meaning any internet-exposed instance running a vulnerable version is at risk without any attacker credential requirements. This incident highlights the danger of delaying patches for internet-facing collaboration platforms, where exploitation timelines from disclosure to active attack can be extremely short. The presence of webshells also indicates attackers intend persistent, long-term access — making rapid detection and response equally as critical as patching.

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Indicators of Compromise

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  • cve — CVE-2026-110447

Entities

Collabora Online - Built-in CODE Server (product)Nextcloud (product)Collabora (vendor)PHP webshells (technology)Second Security (vendor)