id: PYSEC-2026-2431
published: "2026-07-13T14:36:47.243344Z"
modified: "2026-07-13T16:03:49.106101Z"
aliases:
- CVE-2026-33752
- GHSA-qw2m-4pqf-rmpp
summary: "curl_cffi: Redirect-based SSRF leads to internal network access in curl_cffi (with TLS impersonation bypass)"
details: "### Summary\ncurl_cffi does not restrict requests to internal IP ranges, and follows redirects automatically via the underlying libcurl.\n\nBecause of this, an attacker-controlled URL can redirect requests to internal services such as cloud metadata endpoints. In addition, curl_cffi’s TLS impersonation feature can make these requests appear as legitimate browser traffic, which may bypass certain network controls.\n\n### Details\nThe issue comes from how curl_cffi handles outbound requests\n- User-supplied URLs are passed directly to libcurl without checking whether they resolve to internal IP ranges (e.g., 127.0.0.1, 169.254.0.0/16).\n- Redirects are automatically followed (CURLOPT_FOLLOWLOCATION = 1) inside libcurl.\n- There is no validation of redirect destinations at the Python layer.\n\nThis means that even if an application only allows requests to external URLs, an attacker can\n- Provide a URL pointing to an attacker-controlled server\n- Return a redirect response pointing to an internal service\n- Have curl_cffi follow that redirect automatically\n\nAs a result, internal endpoints (such as cloud instance metadata APIs) can be accessed.\n\nAdditionally, curl_cffi supports TLS fingerprint impersonation (e.g., impersonate=\"chrome\"). In environments where outbound requests are filtered based on TLS fingerprinting, this can make such requests harder to detect or block\n\nThis behavior is similar to previously reported redirect-based SSRF issues such as CVE-2025-68616, where redirects allowed access to unintended internal resources.\n\n### PoC\n1. Direct internal request\n```\nimport curl_cffi\nresp = curl_cffi.get(\"http://169.254.169.254/latest/meta-data/\")\nprint(resp.text)\n```\n2. Redirect to internal service\nAttacker server:\n```\nGET /test\n→ 302 Location: http://169.254.169.254/latest/meta-data/\n```\nVictim code:\n```\nimport curl_cffi\nresp = curl_cffi.get(\"https://attacker.example/test\")\nprint(resp.text)\n```\nResult\n- Initial request goes to attacker server\n- Redirect is returned\n- libcurl follows the redirect automatically\n- Internal metadata endpoint is accessed\n\n3. With TLS impersonation\n```\nimport curl_cffi\\\nresp = curl_cffi.get(\n    \"https://attacker.example/test\",\n    impersonate=\"chrome\")\n```\nIn some environments, this may help the request bypass TLS-based filtering controls.\n\n\n### Impact\nAn attacker who can control the requested URL may be able to:\n- Access internal network services\n- Reach cloud metadata endpoints and retrieve sensitive information\n- Bypass certain outbound filtering mechanisms (depending on environment)\nThis corresponds to CWE-918 Server-Side Request Forgery."
affected:
- package:
    name: curl-cffi
    ecosystem: PyPI
    purl: pkg:pypi/curl-cffi
  ranges:
  - type: ECOSYSTEM
    events:
    - introduced: "0"
    - fixed: 0.15.0
  versions:
  - 0.1.5
  - 0.10.0
  - 0.10.0b1
  - 0.10.0b2
  - 0.11.0
  - 0.11.0b1
  - 0.11.0b2
  - 0.11.1
  - 0.11.2
  - 0.11.3
  - 0.11.4
  - 0.12.0
  - 0.12.0b1
  - 0.12.1b1
  - 0.12.1b2
  - 0.13.0
  - 0.13.0b1
  - 0.14.0
  - 0.14.0b1
  - 0.14.0b2
  - 0.14.0b3
  - 0.14.0b4
  - 0.14.0b5
  - 0.15.0b1
  - 0.15.0b2
  - 0.15.0b3
  - 0.15.0b4
  - 0.15.0b5
  - 0.15.0b6
  - 0.15.0rc1
  - 0.2.0
  - 0.2.1
  - 0.2.4
  - 0.2.5
  - 0.3.0
  - 0.3.1
  - 0.3.2
  - 0.3.7
  - 0.3.8
  - 0.4.0
  - 0.5.0
  - 0.5.1
  - 0.5.10
  - 0.5.10b1
  - 0.5.10b2
  - 0.5.10b3
  - 0.5.10b4
  - 0.5.10b5
  - 0.5.2
  - 0.5.3
  - 0.5.4
  - 0.5.5
  - 0.5.6
  - 0.5.7
  - 0.5.9
  - 0.5.9b1
  - 0.5.9b2
  - 0.5.9b3
  - 0.5.9b4
  - 0.5.9b5
  - 0.5.9b6
  - 0.6.0
  - 0.6.0b2
  - 0.6.0b4
  - 0.6.0b7
  - 0.6.0b9
  - 0.6.1
  - 0.6.2
  - 0.6.3
  - 0.6.3b1
  - 0.6.4
  - 0.7.0
  - 0.7.0b4
  - 0.7.0b6
  - 0.7.0b7
  - 0.7.1
  - 0.7.2
  - 0.7.3
  - 0.7.3b1
  - 0.7.4
  - 0.8.0b1
  - 0.8.0b3
  - 0.8.0b6
  - 0.8.0b7
  - 0.8.1b8
  - 0.8.1b9
  - 0.9.0
  - 0.9.0b1
  - 0.9.0b2
references:
- type: WEB
  url: https://github.com/lexiforest/curl_cffi/security/advisories/GHSA-qw2m-4pqf-rmpp
- type: ADVISORY
  url: https://nvd.nist.gov/vuln/detail/CVE-2026-33752
- type: PACKAGE
  url: https://github.com/lexiforest/curl_cffi
- type: PACKAGE
  url: https://pypi.org/project/curl-cffi
- type: ADVISORY
  url: https://github.com/advisories/GHSA-qw2m-4pqf-rmpp
severity:
- type: CVSS_V3
  score: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N