Security readout for executives and security teams
Plain-English summary
CVE-2021-3773 is an information exposure flaw in Linux netfilter. A network-connected attacker may infer OpenVPN connection endpoint information, which could help plan other network attacks. The sources do not provide CVSS, a named patch, or confirmed active exploitation.
Executive priority
Prioritize if the organization operates exposed OpenVPN infrastructure on affected Linux kernels. The business risk is reconnaissance and privacy loss rather than confirmed remote code execution, but missing severity data limits certainty.
Technical view
The issue is classified as CWE-200 and affects listed Linux kernel builds: 5.14.0-49.el9, 5.15.15-100.fc34, and 5.15.15-200.fc35. The described impact is endpoint information inference related to OpenVPN through netfilter behavior. Vendor references exist, but source detail is limited.
Likely exposure
Likely exposure is Linux systems running the listed affected kernel builds, especially OpenVPN endpoints or gateways relying on netfilter. Oracle and NetApp references suggest downstream vendor impact should be checked, but the bundle does not enumerate every affected product.
Exploitation context
The CVE record describes a network-connected attacker inferring OpenVPN endpoint information for use in traditional network attacks. CISA KEV status is false in the bundle, and no cited source here confirms active exploitation.
Researcher notes
Evidence is sparse: no CVSS vector, no exploit confirmation, and no explicit fix text in the bundle. Focus validation on affected kernel lineage, OpenVPN exposure, vendor advisory mapping, and whether downstream appliances include vulnerable Linux kernel components.
Mitigation direction
- Check Red Hat, Oracle, NetApp, and OS vendor advisories for fixed kernel packages.
- Prioritize review of internet-facing or partner-facing OpenVPN gateways.
- Inventory systems running the listed kernel builds.
- Apply vendor-supported kernel updates when available.
- Reduce unnecessary network reachability to VPN infrastructure.
Validation and detection
- Identify OpenVPN systems using Linux netfilter.
- Record kernel versions and compare against listed affected builds.
- Review vendor advisories for matching product and package status.
- Confirm updated kernels are deployed after patching.
- Monitor VPN and firewall logs for unusual reconnaissance activity.
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.
CWE-200: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-3773 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://bugzilla.redhat.com/show_bug.cgi?id=2004949CVE reference
- https://www.oracle.com/security-alerts/cpujul2022.htmlCVE reference
- https://citizenlab.ca/2024/07/vulnerabilities-in-vpns-paper-presented-at-the-privacy-enhancing-technologies-symposium-2024/CVE reference
- https://security.netapp.com/advisory/ntap-20250328-0004/CVE reference
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.
Exposure of Sensitive Information to an Unauthorized Actor
Exposure of Sensitive Information to an Unauthorized Actor represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.