CVE-2018-1172
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 · uneditedThis vulnerability allows remote attackers to deny service on vulnerable installations of The Squid Software Foundation Squid 3.5.27-20180318. Authentication is not required to exploit this vulnerability. The specific flaw exists within ClientRequestContext::sslBumpAccessCheck(). A crafted request can trigger the dereference of a null pointer. An attacker can leverage this vulnerability to create a denial-of-service condition to users of the system. Was ZDI-CAN-6088.
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 confidenceA remote, unauthenticated attacker can send a crafted HTTPS request to vulnerable Squid proxy installations that triggers a null pointer dereference in the ClientRequestContext::sslBumpAccessCheck() function, causing the service to crash and creating a denial-of-service condition.
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= 3.5.27CVSS 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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Identify Squid versionRun `squid -v` or `squid -V` to display the installed Squid version informationAffected if The displayed version is exactly 3.5.27 (the only version listed as affected)
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Verify SSL bumping feature is activeExamine the Squid configuration file (commonly at /etc/squid/squid.conf) for any `ssl_bump` directivesAffected if Any ssl_bump rule is present in the configuration, as the vulnerability exists in the sslBumpAccessCheck() code path
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Confirm HTTPS interception is configuredSearch the Squid configuration for related SSL inspection settings such as `https_port` with `ssl-bump` flags, or `sslproxy_flags`Affected if HTTPS traffic interception or SSL bumping is explicitly configured, enabling the vulnerable code path
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Check Squid service statusVerify the Squid service is actively running using `systemctl status squid` or `service squid status`Affected if Squid is running with the affected version and SSL bumping enabled, the service is vulnerable to the null pointer dereference crash
The environment is affected if Squid version 3.5.27 is installed AND SSL bumping (ssl_bump) is enabled in the configuration, allowing crafted HTTPS requests to crash the 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 dataApply the Squid security update/patch for CVE-2018-1172 or upgrade to a patched version of Squid that addresses this vulnerability.
- Consultation1.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,904.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-1172 — 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-2018-1172 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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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.
- 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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