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Ubuntu LinuxOperating system · Canonical

CVE-2016-4054

HIGH · 8.1 CVSS v3.0 Published 2016-04-25
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
90/100
Remediation priority · Urgent
High EPSS Remotely reachable No privileges Zero-click

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 · unedited
Buffer overflow in Squid 3.x before 3.5.17 and 4.x before 4.0.9 allows remote attackers to execute arbitrary code via crafted Edge Side Includes (ESI) responses.

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 · high confidence

Buffer overflow vulnerability in Squid proxy server's Edge Side Includes (ESI) parser allows remote attackers to execute arbitrary code via specially crafted ESI responses. Affects Squid 3.x before 3.5.17 and 4.x before 4.0.9.

MitigationUpgrade to Squid 3.5.17/4.0.9 or later to patch the buffer overflow. If immediate upgrade is not feasible, consider disabling ESI processing or implementing additional input validation at upstream filters.

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
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 15.10= 16.04
LinuxOperating system
Affected:= 6= 7
SquidApplication
Affected:= 3.0= 3.1= 3.1.0.1= 3.1.0.2= 3.1.0.3= 3.1.0.4= 3.1.0.5= 3.1.0.6= 3.1.0.7= 3.1.0.8= 3.1.0.9= 3.1.0.10

CVSS 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
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check if Squid is installed
    Run command: squid -v 2>/dev/null || dpkg -l | grep squid || rpm -qa | grep squid
    Affected if Squid is not installed means not affected, but if installed proceed to next checks
  2. Determine Squid version
    Run: squid -v 2>&1 | head -1 or check output from dpkg/rpm query
    Affected if Version is 3.x before 3.5.17 OR version is 4.x before 4.0.9 means affected
  3. Check if ESI processing is enabled
    Examine Squid configuration file (typically /etc/squid/squid.conf) for esi parser directives; run: grep -i 'esi' /etc/squid/squid.conf 2>/dev/null
    Affected if If ESI is explicitly disabled (esi_parser false or similar), the attack surface is reduced but version still matters for complete assessment
  4. Verify configuration allows ESI responses from upstream
    Review squid.conf for any proxy configurations that allow upstream responses to be processed as ESI; check acl rules for backend sources
    Affected if Squid configured to process ESI from untrusted upstream sources means likely vulnerable if version is in affected range

User is affected if Squid version is 3.x before 3.5.17 or 4.x before 4.0.9 AND ESI processing is enabled in the configuration.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Squid 3.5.17/4.0.9 or later to patch the buffer overflow. If immediate upgrade is not feasible, consider disabling ESI processing or implementing additional input validation at upstream filters.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-4054 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data