Security readout for executives and security teams
Plain-English summary
This issue lets an unauthenticated attacker abuse a vulnerable Bitdefender GravityZone relay/update service as a server-side request proxy. The main business risk is confidentiality: the CVSS vector indicates high potential data exposure, with no stated integrity or availability impact.
Executive priority
Handle as a moderate confidentiality risk for organizations using Bitdefender GravityZone relay mode. Prioritize confirmation and upgrade, especially where relay/update services are reachable beyond tightly controlled internal networks.
Technical view
CVE-2021-3959 is a CWE-918 SSRF in the EPPUpdateService component of Bitdefender Endpoint Security Tools. It affects Bitdefender GravityZone versions before 3.3.8.272 when operating as an update server in relay mode. CVSS 3.1 is 6.8, with network access, high attack complexity, no privileges, no user interaction, changed scope, and high confidentiality impact.
Likely exposure
Relevant exposure is limited to environments running Bitdefender GravityZone relay/update server components before 3.3.8.272. The source bundle does not provide CPEs, deployment prevalence, or default exposure details.
Exploitation context
The bundle does not cite active exploitation, and KEV is false. The vulnerability is remotely reachable and unauthenticated, but rated high complexity. Treat exposed relay-mode update servers as priority validation targets.
Researcher notes
Evidence supports SSRF impact in EPPUpdateService and a fixed threshold of 3.3.8.272. Public evidence in the bundle is limited; it does not establish exploit availability, exploitation in the wild, CPE coverage, or detailed attack preconditions beyond the CVSS vector.
Mitigation direction
- Upgrade affected Bitdefender GravityZone components to version 3.3.8.272 or later.
- Review Bitdefender advisory VA-10145 for vendor-specific remediation guidance.
- Inventory relay-mode update servers and remove unsupported vulnerable versions.
- Limit relay/update service exposure to required endpoint and management networks.
- Monitor vulnerable-era relay servers for unusual proxy-like request patterns.
Validation and detection
- Confirm whether GravityZone relay/update server mode is enabled anywhere.
- Record installed GravityZone and Endpoint Security Tools component versions.
- Verify all relevant systems are at 3.3.8.272 or later.
- Check network paths to relay/update services from untrusted segments.
- Document any remaining exceptions and compensating controls.
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-918: 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 lookupCloud metadata behavior lookup
The CVE wording references SSRF or metadata access, so cloud discovery and credential material review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-3959 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
- Medium
- CVSS
- 6.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
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 vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N2.24Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.8MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.bitdefender.com/support/security-advisories/server-side-request-forgery-in-bitdefender-gravityzone-update-server-in-relay-mode-va-10145CVE 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.
Server-Side Request Forgery (SSRF)
Server-Side Request Forgery (SSRF) represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.