Plex Media Server Remote Code Execution
CVE-2020-5741 is a high-severity deserialization of untrusted data vulnerability in Plex Media Server (Windows), with a CVSS 3.1 base score of 7.2 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. Affected Plex Media Server (Windows) versions: Versions prior to 1.19.3. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on March 10, 2023, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update Media Server to 1.19.3 or a later version.
- CISA's required action: Apply updates per vendor instructions.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Plex Media Server (Windows) | Plex Media Server (Windows) | Versions prior to 1.19.3 | Not stated |
| Plex | Media Server | before 1.19.3 | 1.19.3 |
Version data comes from the organisation that assigned the CVE. 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
- HighAdministrator-level access is required first.
- 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:H/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.2 | High | NVD |
| CVSS 3.1 | 7.2 | High | CISA (ADP) |
| CVSS 2.0 | 6.5 | Medium | NVD |
Official description
Deserialization of Untrusted Data in Plex Media Server on Windows allows a remote, authenticated attacker to execute arbitrary Python code.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Deserialization of Untrusted Data
The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.
How developers prevent this class of flaw
- If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
- When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
- Explicitly define a final object() to prevent deserialization.
More Deserialization of Untrusted Data vulnerabilities (CWE-502)
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: no, 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-2020-5741US Government Resource
Technical write-ups (may include proof of concept)
- packetstormsecurity.com/files/158470/Plex-Unpickle-Dict-Windows-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
- tenable.com/security/research/tra-2020-32Exploit, Third Party Advisory
Recent Deserialization of Untrusted Data vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 8.8 High severity
- 9.8 Critical severity
- 9.8 Critical severity
- 8.8 High severity
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