UK NCSC recommends orgs to fix CVE-2020

Microsoft Office contains a memory corruption flaw (CWE-399) in its handling of Rich Text Format (RTF) files, allowing a crafted RTF document to corrupt memory when the file is parsed. The flaw is triggered by opening a specially crafted RTF file — typically delivered as an email attachment — in an affected version of Microsoft Office. Successful exploitation yields remote code execution in the context of the current user, so attacker privilege is limited to the rights of the logged-in account. Per the CISA data, Microsoft Office is the affected product, with no specific version ranges provided; the flaw was fixed in Microsoft's April 2015 Patch Tuesday security updates (MS15-033), so risk is concentrated on systems that never applied those updates. Exploitation is confirmed in the wild — the CVE was added to the CISA KEV on 2021-11-03 (ransomware use unknown) — it carries a 96.8% EPSS probability of exploitation within 30 days (100th percentile), and related reporting links RTF exploit techniques of this era to targeted APT campaigns (e.g., the T9000 backdoor and DragonOK tooling).

Do: Apply Microsoft's April 2015 Office security updates (MS15-033) on all endpoints, per the CISA KEV required action, prioritizing hosts running older Office editions, and verify installation via installed-updates checks. As interim hardening, treat inbound RTF files with suspicion (block or sandbox RTF email attachments) and monitor for suspicious child processes spawned by Word (e.g., Winword.exe launching cmd.exe or PowerShell) to detect possible prior exploitation. Organizations still on legacy Office versions should upgrade to currently supported editions that receive ongoing security updates.

A remote code execution vulnerability exists in Microsoft SharePoint when the software fails to check the source markup of an application package. An attacker who successfully exploited the vulnerability could run arbitrary code in the context of the SharePoint application pool and the SharePoint server farm account. Exploitation of this vulnerability requires that a user uploads a specially crafted SharePoint application package to an affected version of SharePoint. The security update addresses the vulnerability by correcting how SharePoint checks the source markup of application packages.