CurlApplication · Haxx
CVE-2026-9079
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 · uneditedlibcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the old credentials around to get used for subsequent transfers that should not know nor use them.
In the news
Third-party coverageSurfaced from public web coverage — external links open in a new tab.
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 confidencelibcurl contains a flaw where instructing it to clear proxy authentication credentials fails to actually clear them, leaving old credentials in memory where they get automatically reused for subsequent transfers that should not have access to those credentials.
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
>= 8.8.0, < 8.21.0CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/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 checksWork through these to decide whether this CVE applies to you.
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Determine installed libcurl versionRun 'curl --version' or check your application's linked libcurl library version using 'ldd' or dependency inspection toolsAffected if Version is greater than or equal to 8.8.0 and less than 8.21.0
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Verify proxy authentication is in useInspect application configuration files, environment variables (HTTP_PROXY, HTTPS_PROXY, ALL_PROXY), or runtime logs for proxy authentication credentials being setAffected if Proxy authentication credentials (username/password) are configured for outgoing connections
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Check for credential reuse across different proxy targetsReview application flow to determine if proxy credentials set for one connection are reused for subsequent different proxy destinationsAffected if The application uses the same libcurl handle or pool for multiple proxy connections after clearing credentials
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Inspect memory behavior during credential clearingIf you have access to the application runtime, observe that after issuing a credential clear command (CURLOPT_PROXYAUTH with CURLAUTH_NONE or similar), the previous credentials remain accessible in memoryAffected if Old proxy credentials remain in memory and are automatically reapplied to new requests after a clear instruction was issued
You are affected if your libcurl version is between 8.8.0 and 8.20.x inclusive and your application uses proxy authentication with potential credential reuse across different proxy targets.
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.
dbcve · scoped8.21.0
Update libcurl to the patched version that properly clears proxy authentication credentials when instructed. Review application logs for any evidence of unauthorized proxy usage during the vulnerable period.
curl 8.21.0 or later
- Check current curl version by running: curl --version
- Upgrade curl to version 8.21.0 or later. For Linux/Unix systems using package managers, use: apt-get update && apt-get install curl (Debian/Ubuntu) or yum update curl (RHEL/CentOS) or dnf update curl (Fedora)
- For macOS, use: brew upgrade curl
- For Windows, download the latest curl release from https://curl.se/windows/
- Verify the upgrade was successful by running: curl --version and confirming the version is 8.21.0 or higher
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Curl
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 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 $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-9079 — 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-2026-9079 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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