Security readout for executives and security teams
Plain-English summary
CVE-2018-6332 is a denial-of-service weakness in HHVM deployments using Proxygen for HTTP/2. Invalid HTTP/2 settings can make the server consume disproportionate resources, potentially reducing availability. The issue is medium severity because exploitation requires higher complexity, but exposed internet-facing services could still face outage risk.
Executive priority
Address during normal vulnerability remediation, with faster handling for public HHVM Proxygen HTTP/2 services that support business-critical availability. There is no sourced evidence of active exploitation, but the potential impact is service disruption.
Technical view
The vulnerability is classified as CWE-400 resource consumption. It affects supported HHVM versions described as 3.24.3, 3.21.7, and below when Proxygen handles HTTP/2 requests. CVSS 3.1 is 5.9 with network attack vector, no privileges, no user interaction, high attack complexity, and availability impact only.
Likely exposure
Exposure is limited to HHVM services that use the Proxygen server to process HTTP/2 traffic. Systems not running HHVM, not using Proxygen, or not accepting HTTP/2 through Proxygen are not indicated as affected by the provided sources.
Exploitation context
The source bundle does not show CISA KEV listing or public active exploitation evidence. The vulnerability is remotely reachable where HTTP/2 is exposed, but the CVSS vector marks attack complexity high. Treat it as an availability risk rather than a confidentiality or integrity issue.
Researcher notes
Evidence is narrow: the CVE description provides the affected condition and CVSS vector, and the only vendor reference is the HHVM 3.25 release blog. The bundle contains inconsistent affected-version metadata, so validate against vendor guidance before making version-based closure decisions.
Mitigation direction
- Inventory HHVM deployments and identify Proxygen HTTP/2 use.
- Review HHVM 3.25 release guidance and current vendor advisories.
- Prioritize updates for internet-facing HHVM Proxygen services.
- Disable or restrict HTTP/2 exposure if vendor-approved and operationally safe.
- Monitor capacity and error rates during remediation.
Validation and detection
- Confirm HHVM version on each relevant host or container.
- Verify whether Proxygen handles HTTP/2 on exposed routes.
- Check logs for abnormal HTTP/2 negotiation errors and resource spikes.
- Confirm updated systems no longer match the affected version description.
- Document any compensating controls for services awaiting update.
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-400: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. 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-2018-6332 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
- 5.9 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
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:U/C:N/I:N/A:H2.23.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.9MediumVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://hhvm.com/blog/2018/03/15/hhvm-3.25.htmlCVE 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.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.