Security readout for executives and security teams
Plain-English summary
This CVE affects older H2O web server releases and can let a remote attacker crash or degrade the service. The available sources describe denial of service, not data theft or code execution. Business urgency depends on whether affected H2O versions are internet-facing or support critical customer traffic.
Executive priority
Prioritize remediation for internet-facing or revenue-critical H2O services. The known impact is service disruption, and the absence of CVSS or exploit evidence lowers certainty, not operational relevance.
Technical view
H2O 2.0.3 and earlier, and 2.1.0-beta2 and earlier, are affected. The issue is triggered by format string specifiers in a template file through fastcgi, mruby, proxy, redirect, or reproxy handling. Public source data does not provide CVSS, CWE, or detailed fixed-version evidence.
Likely exposure
Exposure is most likely where affected H2O versions are deployed as public web front ends, reverse proxies, or application gateways using the named template-related features. Internal-only H2O instances still matter if they support important services.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. Treat this as a remote availability risk with incomplete public severity data, not as confirmed exploited-in-the-wild activity.
Researcher notes
Public data identifies affected version ranges and feature areas but lacks CVSS, CWE, patch-version detail, and exploitation evidence. Avoid assuming broader impact beyond denial of service unless vendor materials confirm it.
Mitigation direction
- Inventory H2O deployments and identify versions 2.0.3 or earlier and 2.1.0-beta2 or earlier.
- Check H2O and JVN guidance for the fixed release and recommended remediation.
- Prioritize upgrades or replacement for internet-facing and business-critical H2O services.
- Review use of fastcgi, mruby, proxy, redirect, and reproxy features in affected deployments.
- Ensure monitoring alerts on H2O crashes, restart loops, and abnormal error spikes.
Validation and detection
- Confirm installed H2O version from package, container, or build metadata.
- Map whether the instance is externally reachable or supports critical internal workflows.
- Review configuration for fastcgi, mruby, proxy, redirect, or reproxy usage.
- Check operational logs for unexplained crashes or denial-of-service symptoms.
- Document compensating controls if immediate upgrade is not possible.
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.
CVE-2016-4864 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://github.com/h2o/h2o/issues/1077CVE reference · x_refsource_CONFIRM
- JVN#94779084CVE reference · third-party-advisory, x_refsource_JVN
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.