Microsoft Issues Patches for Actively Exploited Excel, Exchange Server 0

Microsoft Virtual Machine Bus (VMBus) Remote Code Execution Vulnerability

In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the "out" parameter can be NULL and, on exit, the "outlen" parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the "out" parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call. This can lead to a buffer overflow when EVP_PKEY_decrypt() is called by the application a second time with a buffer that is too small. A malicious attacker who is able present SM2 content for decryption to an application could cause attacker chosen data to overflow the buffer by up to a maximum of 62 bytes altering the contents of other data held after the buffer, possibly changing application behaviour or causing the application to crash. The location of the buffer is application dependent but is typically heap allocated. Fixed in OpenSSL 1.1.1l (Affected 1.1.1-1.1.1k).

Microsoft Excel, a component of Microsoft Office, contains a security feature bypass (CWE-357, insufficient verification of data authenticity) that would allow a local user to achieve arbitrary code execution. The flaw is triggered when Excel fails to properly verify data authenticity, allowing a file handled by Excel to bypass one of its security features rather than being processed safely. Successful exploitation lets an attacker run arbitrary code in the context of the local user, typically requiring the user to open Excel content on their machine. Anyone running the affected Microsoft Office/Excel software is exposed; the source data does not specify affected version ranges or fixed builds. The vulnerability was added to CISA's Known Exploited Vulnerabilities catalog on 2021-11-17, confirming in-the-wild exploitation, and it carries a high 43% EPSS probability of exploitation within 30 days (99th percentile), though no public proof-of-concept is known and ransomware use is unknown.

Do: Apply Microsoft's security updates for Office/Excel addressing CVE-2021-42292 per vendor instructions (the November 2021 Patch Tuesday release; the source data does not list specific fixed versions, so check Microsoft's advisory for affected builds). Federal agencies must patch by the CISA KEV required deadline. Until patched, exercise caution opening Excel files from untrusted or internet-sourced locations, since exploitation requires local user interaction.

Microsoft Defender Remote Code Execution Vulnerability

Microsoft Dynamics 365 On-Premises Remote Code Execution Vulnerability

CVE-2021-42321 is an insecure deserialization remote code execution flaw in on-premises Microsoft Exchange Server, tied to insufficient validation by Exchange's ChainedSerializationBinder. Per the CVSS vector, it is triggered over the network by an authenticated user with low privileges and no user interaction, by submitting crafted serialized data that Exchange fails to safely deserialize. A successful attacker gains arbitrary code execution on the Exchange server with high impact to confidentiality, integrity, and availability, giving a foothold in the mail environment. Organizations running affected on-premises Exchange deployments are in scope. The flaw was actively exploited before patches shipped in November 2021, has public PoC exploits, was added to CISA's KEV on 2021-11-17 with known ransomware use, and carries an EPSS of 91.7% (99.9+ percentile).

Do: Apply the November 2021 Microsoft Exchange Server security updates per vendor instructions to affected on-premises Exchange 2016/2019 deployments. Given confirmed in-the-wild exploitation and known ransomware use, check Exchange servers for signs of compromise, verify backups, and review accounts holding privileged Exchange roles, since exploitation requires authenticated access — enforce MFA and audit impersonation/admin role assignments while patching.

Visual Studio Code Elevation of Privilege Vulnerability

3D Viewer Remote Code Execution Vulnerability