Security readout for executives and security teams
Plain-English summary
Older Nagios XI systems have a flaw that can let an already-authenticated administrator place executable files on the server. Because this can become remote code execution, compromise of an admin account could become compromise of the monitoring host.
Executive priority
Treat this as high priority for Nagios XI environments. The vulnerability requires admin access, but monitoring platforms are high-value infrastructure, and RCE on them can support deeper operational compromise.
Technical view
CVE-2021-3277 affects Nagios XI 5.7.5 and earlier. The custom-includes rename functionality improperly validates file handling, allowing authenticated admins to upload arbitrary files. The public description states PHP files can be uploaded, leading to remote code execution.
Likely exposure
Exposure is limited to Nagios XI 5.7.5 and earlier, especially instances where admin access is reachable over the network. The source bundle does not identify other affected products or exact fixed versions.
Exploitation context
A public technical write-up exists, and the CVE description describes an RCE outcome. The bundle does not show CISA KEV listing or other evidence of active exploitation. The attack requires authenticated administrator access based on the provided sources.
Researcher notes
The provided data lacks CVSS, CWE, detailed affected CPEs, and a named patch version. Analysis is therefore grounded on the CVE description and the linked public write-up only. Avoid assuming unauthenticated exploitability or active exploitation.
Mitigation direction
- Check Nagios vendor guidance for the fixed release and upgrade path.
- Restrict Nagios XI administrative access to trusted networks and users.
- Audit and remove unnecessary or stale administrator accounts.
- Inspect custom-includes and web-accessible paths for unauthorized executable files.
- Monitor Nagios XI admin actions and unexpected file changes.
Validation and detection
- Inventory all Nagios XI instances and record their versions.
- Flag any Nagios XI deployment running 5.7.5 or earlier.
- Review administrator account activity around custom include changes.
- Check for unexpected PHP or executable files in custom-includes paths.
- Confirm whether vendor remediation has been applied.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
Execution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-3277 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://asaf.me/2021/01/21/nagios-xi-5-7-5-remote-code-execution/CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.