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CVE-2026-67339 medium CVSS 5.3

Information Disclosure in guzzlehttp/guzzle (CVE-2026-67339)

Summary

Vulnerability in guzzlehttp/guzzle (CVE-2026-67339). Risk of unauthorized operations or information disclosure. Exploitable via CurlHandler. Mitigation: upgrade to 7.14.2 or later.

Original description

The description as published by the source.

Impact

In affected versions, the built-in cURL handlers (CurlHandler and CurlMultiHandler) put every first-class request header in cURL's origin header list (CURLOPT_HTTPHEADER). These handlers are the default when the PHP cURL extension is available. They move Proxy-Authorization to the proxy-only list (CURLOPT_PROXYHEADER) only when Guzzle predicts an HTTP or HTTPS proxy. A "first-class" header is part of the normal request message and can be set on a PSR-7 request, through client headers defaults, the headers request option, or middleware. It does not include a literal line supplied through raw CURLOPT_HTTPHEADER, CURLOPT_PROXYHEADER, or stream_context.http.header controls.

Because that migration follows Guzzle's prediction rather than the route libcurl actually takes, the credential stays in the origin list and is sent to the origin server when a request is:

  • direct, including proxy set to '' to disable proxying.
  • bypassed by a no, no_proxy, or NO_PROXY match.
  • sent through a SOCKS proxy, which does not use the HTTP proxy header channel.
  • redirected from a safely proxied hop into any of those routes: redirect middleware re-evaluates the proxy per hop but, unlike Authorization and Cookie, does not strip Proxy-Authorization cross-origin.

On installations whose libcurl is older than 7.37.0, or whose PHP cURL extension lacks CURLOPT_PROXYHEADER, CURLOPT_HEADEROPT, and CURLHEADER_SEPARATE, no proxy-only channel is available…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-67339 has been found in guzzlehttp/guzzle.
Attackers can target a specific entry point like CurlHandler over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade guzzlehttp/guzzle to 7.14.2 or later.
If unsure, ask your IT team or search "guzzlehttp/guzzle CVE-2026-67339" on the vendor's site.

CVE-2026-67339 (guzzlehttp/guzzle) — CWE-200 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: CurlHandler / CurlMultiHandler / CURLOPT_HTTPHEADER / CURLOPT_PROXYHEADER
Patched: 7.14.2 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Information disclosure (CWE-200) exists in guzzlehttp/guzzle. Attackers reach the vulnerable code path via CurlHandler without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of guzzlehttp/guzzle. Attack surface: CurlHandler / CurlMultiHandler / CURLOPT_HTTPHEADER / CURLOPT_PROXYHEADER.

🔥 Severity

Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 7.14.2.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'guzzlehttp/guzzle' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'guzzlehttp/guzzle' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で guzzlehttp/guzzle を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade guzzlehttp/guzzle to 7.14.2

    ステージング環境で 7.14.2 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

composer guzzlehttp/guzzle
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.14.2"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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