Security readout for executives and security teams
Plain-English summary
CVE-2018-6340 is a high-severity HHVM memory-safety flaw in Memcache::getextendedstats. It can cause an out-of-bounds read, but the source says exploitation requires control over memcached server hostnames or ports. Business urgency is highest where HHVM applications accept or derive memcached endpoints from untrusted input or configuration paths.
Executive priority
Prioritize remediation for internet-facing or multi-tenant HHVM services where memcached endpoint selection is dynamic. Lower urgency may be reasonable for isolated systems with fixed, trusted memcached configuration.
Technical view
The issue is CWE-125 out-of-bounds read in HHVM's Memcache::getextendedstats. The CVSS 3.1 score is 8.1, with network attack vector but high attack complexity. The source bundle says affected supported HHVM versions include 3.30 and 3.27.4 and below, with public HHVM release and GitHub commit references.
Likely exposure
Exposure is likely limited to HHVM deployments using the Memcache extension, especially where memcached hostnames or ports can be influenced by users, tenants, integrations, or unsafe configuration management.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. Exploitation is not described as trivial because attacker control over memcached hostnames or ports is required.
Researcher notes
Evidence supports a high-impact memory-safety bug with constrained prerequisites. The bundle does not provide exploit details, crash conditions, or a definitive fixed-version matrix beyond HHVM release and commit references, so validation should focus on version, code usage, and endpoint-control paths.
Mitigation direction
- Identify HHVM systems using Memcache::getextendedstats or related Memcache extension paths.
- Review HHVM 3.30.1 release guidance and the referenced fix commit.
- Upgrade or patch HHVM according to vendor-supported guidance.
- Restrict who can control memcached hostnames and ports.
- Treat memcached endpoint configuration as trusted-only operational data.
Validation and detection
- Inventory running HHVM versions across production and staging.
- Search application code for Memcache::getextendedstats usage.
- Review configuration flows for user-controlled memcached hostnames or ports.
- Confirm patched HHVM builds include the referenced upstream commit.
- Check logs for unexpected memcached endpoint values.
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-125: 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-2018-6340 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
- High
- CVSS
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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:H/I:H/A:H2.25.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://hhvm.com/blog/2018/12/18/hhvm-3.30.1.htmlCVE reference · x_refsource_MISC
- https://github.com/facebook/hhvm/commit/4bff3bfbe90d10451e4638c2118d1ad1117bb3e3CVE 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.
Out-of-bounds Read
Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.