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0xCERT Security Advisory 0xCERT-2026-0225
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Advisory-ID:  0xCERT-2026-0225
Severity:     Medium
Published:    2026-04-04T06:38:11.000Z
Updated:      2026-10-08T22:48:28.126Z
Chains:       Ethereum
URL:          https://www.0xcert.com/advisory/0xCERT-2026-0225

Title: web3.py: SSRF via CCIP Read (EIP-3668) OffchainLookup URL handling

Summary
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web3.py: SSRF via CCIP Read (EIP-3668) OffchainLookup URL handling. web3.py implements CCIP Read / OffchainLookup (EIP-3668) by performing HTTP requests to URLs supplied by smart contracts in offchainlookuppayload["urls"].

Details
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Summary
web3.py implements CCIP Read / OffchainLookup (EIP-3668) by performing HTTP requests to URLs supplied by smart contracts in offchainlookuppayload["urls"]. The implementation uses these contract-supplied URLs directly (after {sender} / {data} template substitution) without any destination validation: - No restriction to https:// (and no opt-in gate for http://) - No hostname or IP allowlist - No blocking of private/reserved IP ranges (loopback, link-local, RFC1918) - No redirect target validation (both requests and aiohttp follow redirects by default) CCIP Read is enabled by default (globalccipreadenabled = True on all providers), meaning any application using web3.

Affected
- - web3 (pip) >= 6.0.0b3, < 7.15.0 — fixed in 7.15.0
- - web3 (pip) = 8.0.0b1 — fixed in 8.0.0b2

Severity
Medium (CVSS 6.9), as rated by the upstream advisory.

Recommended actions
- - Upgrade web3 to 7.15.0 or later
- - Upgrade web3 to 8.0.0b2 or later

Source & attribution
This 0xCERT advisory summarises GHSA-5hr4-253g-cpx2 / CVE-2026-40072 from the GitHub Advisory Database, credited upstream to Nadav0077: https://github.com/advisories/GHSA-5hr4-253g-cpx2. Details may change; refer to the original source for the authoritative record.

References
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- - https://github.com/advisories/GHSA-5hr4-253g-cpx2
- - CVE-2026-40072
- - https://github.com/ethereum/web3.py/security/advisories/GHSA-5hr4-253g-cpx2
- - https://nvd.nist.gov/vuln/detail/CVE-2026-40072
- - https://github.com/ethereum/web3.py/commit/b1c57bb0a124359c9902daaefab4d8af7c3c4c1e

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