CVE-2017-10868
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedH2O version 2.2.2 and earlier allows remote attackers to cause a denial of service in the server via specially crafted HTTP/1 header.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceH2O web server versions 2.2.2 and earlier contain a denial-of-service vulnerability triggered by specially crafted HTTP/1 headers. Remote attackers can send malformed headers that cause the server to crash or become unresponsive, resulting in service unavailability.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 2.2.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Confirm H2O is installedRun 'which h2o' or check for the h2o binary in common paths like /usr/sbin/h2o, /usr/bin/h2o, or look for h2o processes running via 'ps aux | grep h2o'Affected if No h2o binary or process is found, meaning the product is not present
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Determine installed H2O versionRun 'h2o --version' or 'h2o -v' to display the version number. If running as a daemon, check the installed package version via package manager (dpkg -l h2o, rpm -qi h2o, or similar)Affected if Version displayed is 2.2.2 or earlier, or the version cannot be determined but is known to be older than 2.3.0
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Verify HTTP/1 configuration is in useExamine the H2O configuration file (typically /etc/h2o/h2o.conf or /etc/h2o.conf) and look for 'listen:' directives with port 80 or 443, which indicate HTTP/1 handling is enabled. Also check for 'http1: ON' explicitly in the configurationAffected if HTTP/1 listeners are configured and the H2O version is 2.2.2 or earlier; the vulnerability only affects HTTP/1 header processing
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Check for active H2O serviceVerify the h2o service is actively running via 'systemctl status h2o' or 'service h2o status', or check if the port H2O listens on (commonly 80 or 443) is open using 'netstat -tlnp | grep h2o' or 'ss -tlnp | grep h2o'Affected if H2O service is running and bound to a port, combined with version 2.2.2 or earlier, the server is vulnerable to the malformed header DoS
A defender is affected if H2O web server version 2.2.2 or earlier is installed and actively running with HTTP/1 listener configuration, as the malformed HTTP/1 header vulnerability can cause denial of service.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data2.2.3
Upgrade H2O to version 2.3.0 or later which contains the fix for this vulnerability. As a temporary mitigation, implement rate limiting and request validation at a reverse proxy or firewall level.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-10868 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2017-10868 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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