CVE-2026-55568
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 · uneditedGuzzle is an extensible PHP HTTP client. Prior to 7.12.1, in certain configurations, traffic expected to be protected by TLS on the hop to the proxy is transmitted in cleartext. Proxy authentication credentials (the Proxy-Authorization header, proxy userinfo in the proxy URL, or CURLOPT_PROXYUSERPWD) are sent without encryption, and the CONNECT target host and port for tunneled HTTPS requests are exposed. The built-in cURL handlers (GuzzleHttp\Handler\CurlHandler and GuzzleHttp\Handler\CurlMultiHandler, used by default whenever the PHP cURL extension is available) accept an https:// proxy. libcurl older than 7.50.2 silently treats an https:// proxy as a plaintext http:// proxy. The TLS connection to the proxy is never established, and the proxy leg is cleartext with no error or warning. An application is affected when it sends requests through one of the built-in cURL handlers, configures an https:// proxy expecting the proxy connection itself to be encrypted, and runs with libcurl older than 7.50.2. This vulnerability is fixed in 7.12.1.
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 confidenceGuzzle's built-in cURL handlers accept https:// proxy URLs, but libcurl versions older than 7.50.2 silently treat them as plaintext http:// proxies. This causes all proxy traffic including authentication credentials (Proxy-Authorization header, proxy userinfo, CURLOPT_PROXYUSERPWD) and CONNECT tunnel target host/port information to be transmitted in cleartext without any error or warning.
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< 7.12.1CVSS 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
- None
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
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 installed Guzzle versionRun 'composer show guzzlehttp/guzzle' or check your composer.lock file for the guzzlehttp/guzzle package versionAffected if Version is below 7.12.1
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Identify libcurl versionRun 'curl --version' to display the bundled libcurl version, or use phpinfo() to find the curl extension versionAffected if libcurl version is below 7.50.2
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Verify proxy configuration uses HTTPS URLsSearch your codebase for instances of 'https://' appearing after 'proxy' or in CURLOPT_PROXY options, or review environment variables HTTP_PROXY, HTTPS_PROXY, ALL_PROXY for https:// URLsAffected if HTTPS proxy URLs are configured
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Confirm proxy authentication is in useSearch code for CURLOPT_PROXYUSERPWD, Proxy-Authorization header setting, or proxy URLs containing userinfo (@ or : before the @)Affected if Proxy authentication credentials are configured or transmitted
Your environment is affected if Guzzle is below 7.12.1 AND libcurl is below 7.50.2 AND you use an HTTPS proxy URL with authentication credentials, causing those credentials to be sent in cleartext.
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 · scoped7.12.1
Upgrade Guzzle to version 7.12.1 or later, or ensure libcurl 7.50.2 or newer is installed; verify proxy connections are actually encrypted using network traffic analysis.
7.12.1
- Update the Guzzle HTTP client library to version 7.12.1 or later via composer (e.g., composer require guzzlehttp/guzzle:^7.12.1)
- Verify the installed version matches or exceeds 7.12.1 by running composer show guzzlehttp/guzzle
- Test that HTTPS proxy connections are properly establishing TLS to the proxy server
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 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-2026-55568 — 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-2026-55568 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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- Version or environment caveats, and links to real fixes
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