CurlApplication · Haxx
CVE-2017-9502
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 · uneditedIn curl before 7.54.1 on Windows and DOS, libcurl's default protocol function, which is the logic that allows an application to set which protocol libcurl should attempt to use when given a URL without a scheme part, had a flaw that could lead to it overwriting a heap based memory buffer with seven bytes. If the default protocol is specified to be FILE or a file: URL lacks two slashes, the given "URL" starts with a drive letter, and libcurl is built for Windows or DOS, then libcurl would copy the path 7 bytes off, so that the end of the given path would write beyond the malloc buffer (7 bytes being the length in bytes of the ascii string "file://").
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 confidenceHeap-based buffer overflow in libcurl before 7.54.1 on Windows/DOS where the default protocol handler copies file paths 7 bytes beyond the allocated buffer when processing URLs without a scheme that start with a drive letter (e.g., C:path). The overflow occurs because the code miscalculates the copy length when handling file: URLs lacking proper slashes.
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
CurlApplication
<= 7.54.0CVSS 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
- Low
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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 libcurl is installed on Windows/DOSCheck for libcurl.dll in system directories (C:\Windows\System32, C:\Windows\SysWOW64) or search using 'where /r C:\ libcurl.dll' in Command Prompt. Also check installed programs list or package managers like Chocolatey.Affected if libcurl.dll exists on a Windows or DOS system and its version is 7.54.0 or earlier
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Determine installed libcurl versionRun 'curl --version' from Command Prompt or PowerShell. Alternatively, right-click libcurl.dll, select Properties, and check the File Version field.Affected if The reported version is 7.54.0 or any version lower than 7.54.1
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Identify applications using libcurlCheck for applications that bundle or depend on libcurl (common in download managers, file transfer tools, development environments). Search for libcurl.dll in application directories or review application dependencies.Affected if Applications using libcurl are present on the system and process URLs as input
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Determine if URLs without scheme are processedReview application logs, configurations, or code that handles URLs. Look for any processing of URLs in format 'C:path' or 'D:folder\file' without 'file://' prefix, particularly in file transfer or URL-handling contexts.Affected if Any application or service running on the system processes URLs without a scheme that start with a drive letter (e.g., C:data, D:files\doc)
A user is affected if running a Windows/DOS system with libcurl version 7.54.0 or earlier that processes URLs without the file:// scheme which start with a drive letter.
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 libcurl to version 7.54.1 or later. Alternatively, avoid using drive-letter paths as URLs without explicit file:// scheme on Windows/DOS builds.
Fix this in Curl
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 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 $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-9502 — 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-2017-9502 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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