CVE-2016-2390
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 · uneditedThe FwdState::connectedToPeer method in FwdState.cc in Squid before 3.5.14 and 4.0.x before 4.0.6 does not properly handle SSL handshake errors when built with the --with-openssl option, which allows remote attackers to cause a denial of service (application crash) via a plaintext HTTP message.
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 confidenceThe FwdState::connectedToPeer method in Squid's FwdState.cc fails to properly handle SSL handshake errors when Squid is compiled with the --with-openssl option. When a remote attacker sends a plaintext HTTP message to an HTTPS port, the SSL handshake error handling code path triggers an application crash due to improper NULL pointer or error condition handling.
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<= 3.5.13= 4.0.4= 4.0.5CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:H/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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Check installed Squid versionRun 'squid -v' or 'squid -V' to display version information. Look for the version number in the output.Affected if The version shown is 3.5.13 or earlier, or exactly 4.0.4 or 4.0.5
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Verify Squid was compiled with OpenSSL supportRun 'squid -v' and look for '--with-openssl' in the compile options. On Linux, also check 'squid -v 2>&1 | grep -i ssl' or inspect the binary with 'ldd $(which squid) | grep -i ssl'.Affected if OpenSSL support is present (--with-openssl is listed in the build options)
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Confirm Squid is configured to handle HTTPS trafficExamine the Squid configuration file (typically /etc/squid/squid.conf or /etc/squid3/squid.conf) for 'https_port' directives or ACLs referencing SSL/HTTPS ports.Affected if Squid is configured to accept HTTPS connections on any port using the https_port directive
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Identify SSL bump or intercept configurationsSearch the Squid configuration for 'ssl_bump', 'https_port' with 'tls' options, or any SSL certificate configuration directives.Affected if SSL bumping, TLS inspection, or SSL intercept features are enabled in the configuration
You are affected if your Squid version is 3.5.13 or earlier, or 4.0.4/4.0.5, AND it was compiled with OpenSSL support (--with-openssl), AND it is configured to handle HTTPS traffic on any port.
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 dataUpgrade Squid to version 3.5.14 or later, or 4.0.6 or later. If immediate upgrading is not feasible, verify if OpenSSL support is required; if not, rebuild Squid without --with-openssl to disable the vulnerable code path.
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-2390 — 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-2016-2390 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
- No weaponised exploit code, or anything meant to cause harm
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