Vulnerability in guzzlehttp/guzzle (CVE-2026-55568)
Summary
Vulnerability in guzzlehttp/guzzle (CVE-2026-55568). Confidential information can be exposed externally. Exploitable via proxy. Mitigation: upgrade to 7.12.1 or later.
Original description
The description as published by the source.
Guzzle 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.
Source: GitHub Security Advisories (Global) 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-2026-55568 has been found in guzzlehttp/guzzle.
Attackers can target a specific entry point like proxy over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 5.9/10.
What to do: upgrade guzzlehttp/guzzle to 7.12.1 or later.
If unsure, ask your IT team or search "guzzlehttp/guzzle CVE-2026-55568" on the vendor's site.
CVE-2026-55568 (guzzlehttp/guzzle) — CWE-311 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: proxy / http_proxy / https_proxy / HTTPS_PROXY
Patched: 7.12.1 — 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.
A vulnerability (CWE-311) exists in guzzlehttp/guzzle. Attackers reach the vulnerable code path via proxy without authentication.
Check the vendor advisory for the affected versions of guzzlehttp/guzzle. Attack surface: proxy / http_proxy / https_proxy / HTTPS_PROXY.
Severity: Medium (CVSS 5.9/10). Confidential information can be exposed externally.
Update to 7.12.1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
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
-
1Identify 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。 -
2Apply patch patch
Upgrade guzzlehttp/guzzle to 7.12.1ステージング環境で 7.12.1 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。
-
3Post-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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-55568 guzzle
- Ubuntu UBUNTU-CVE-2026-55568 guzzle
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- web github.com