Microsoft .NET Framework Remote Code Execution
CVE-2020-0646 is a critical-severity XML injection vulnerability in Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 from Microsoft, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 versions: Windows 7 for 32-bit Systems Service Pack 1; Windows 7 for x64-based Systems Service Pack 1; Windows 8.1 for 32-bit systems, and others listed below. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on November 3, 2021, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Check which version of Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2 you run against the affected versions below, and install the vendor's latest release.
- CISA's required action: Apply updates per vendor instructions.
- Read the advisory on portal.msrc.microsoft.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE; 26 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 3.1 | 9.8 | Critical | CISA (ADP) |
| CVSS 2.0 | 10.0 | High | NVD |
Official description
A remote code execution vulnerability exists when the Microsoft .NET Framework fails to validate input properly, aka '.NET Framework Remote Code Execution Injection Vulnerability'.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: XML Injection
The product does not properly neutralize special elements that are used in XML, allowing attackers to modify the syntax, content, or commands of the XML before it is processed by an end system.
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Deadline for US federal agencies to remediate, set by CISA.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-0646US Government Resource
Technical write-ups (may include proof of concept)
- packetstormsecurity.com/files/156930/SharePoint-Workflows-XOML-Injection.htmlExploit, Third Party Advisory, VDB Entry
Other vulnerabilities in Microsoft .NET Framework 4.6/4.6.1/4.6.2/4.7/4.7.1/4.7.2
- 7.8 High severity
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