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CVE-2026-67355 medium CVSS 5.9

Vulnerability in guzzlehttp/guzzle (CVE-2026-67355)

Summary

Vulnerability in guzzlehttp/guzzle (CVE-2026-67355). Confidential information can be exposed externally. Exploitable via CookieJar. Mitigation: upgrade to 7.15.1 or later.

Original description

The description as published by the source.

Impact

In affected versions, CookieJar does not preserve whether a response cookie was set without a Domain attribute or with an empty one. A cookie without Domain is host-only and must be returned only to the exact host that set it. Under current cookie processing rules, an empty Domain value is also host-only. Guzzle instead stores the request host in the cookie's Domain field and later applies ordinary domain matching, as though the server had supplied a valid domain. For example, a host-only sid=secret cookie set by example.com can subsequently be sent to child.example.com. FileCookieJar and SessionCookieJar also persist the request host without recording the host-only state, so reloading a jar preserves the widened scope.

An attacker who controls or can observe a child host can therefore receive cookies that were intended only for its parent host. Depending on the cookie, this can disclose session identifiers, authorization tokens, or other sensitive state. Exploitation requires the application to enable Guzzle's cookie support, reuse the same built-in cookie jar, receive a host-only cookie from a parent host, and later make a matching request to a less-trusted child host. The cookie's other restrictions still apply. Its path must match, a Secure cookie is sent only over a secure connection, and an expired cookie is not sent.

Applications that do not use Guzzle's cookie support are not affected. Applications are also not affected by this disc…

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-2026-67355 has been found in guzzlehttp/guzzle.
Attackers can target a specific entry point like CookieJar 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 7.15.1 or later.
If unsure, ask your IT team or search "guzzlehttp/guzzle CVE-2026-67355" on the vendor's site.

CVE-2026-67355 (guzzlehttp/guzzle) — CWE-201 / CVSS v3 5.9
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: CookieJar / Domain / example.com / child.example.com
Patched: 7.15.1 — 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.

❓ What is the problem

A vulnerability (CWE-201) exists in guzzlehttp/guzzle. Attackers reach the vulnerable code path via CookieJar without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of guzzlehttp/guzzle. Attack surface: CookieJar / Domain / example.com / child.example.com.

🔥 Severity

Severity: Medium (CVSS 5.9/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 7.15.1.

🛡️ 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 7.15.1

    ステージング環境で 7.15.1 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。

  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":"7.15.1"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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