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0xCERT Security Advisory 0xCERT-2026-0244
============================================================

Advisory-ID:  0xCERT-2026-0244
Severity:     Medium
Published:    2026-10-15T19:17:33.300Z
Updated:      2026-10-15T20:08:03.748Z
Chains:       Ethereum
URL:          https://www.0xcert.com/advisory/0xCERT-2026-0244

Title: CVE-2026-111171: Web3

Summary
- -------
Web3.py 7.15.0 through 7.16.0 and 8.0.0b2 through 8.0.0 contains a server-side request forgery vulnerability because _check_ip_blocked() does not unwrap IPv4-mapped IPv6 addresses in CCIP Read URL validation. Malicious contracts can return OffchainLookup URLs with IPv4-mapped IPv6 hosts or AAAA records, making clients with CCIP Read enabled send requests to loopback, private, or link-local services.

Details
- -------
Summary
Web3.py 7.15.0 through 7.16.0 and 8.0.0b2 through 8.0.0 contains a server-side request forgery vulnerability because _check_ip_blocked() does not unwrap IPv4-mapped IPv6 addresses in CCIP Read URL validation. Malicious contracts can return OffchainLookup URLs with IPv4-mapped IPv6 hosts or AAAA records, making clients with CCIP Read enabled send requests to loopback, private, or link-local services.

Severity
Medium (CVSS 6.3), as scored by NVD.

Weakness
- - CWE-918

Recommended actions
- - Check whether you run or depend on the affected component and version
- - Apply the vendor's fix or mitigation from the references below

Source & attribution
This 0xCERT advisory summarises CVE-2026-111171 from the U.S. National Vulnerability Database: https://nvd.nist.gov/vuln/detail/CVE-2026-111171. Details may change; refer to the original source for the authoritative record.

References
- ----------
- - https://nvd.nist.gov/vuln/detail/CVE-2026-111171
- - https://github.com/ethereum/web3.py
- - https://github.com/ethereum/web3.py/blob/c8c1ed0c9e77e1a8b74902e6a6825e0b00534b10/web3/utils/ccip_url_validation.py#L16-L57
- - https://github.com/ethereum/web3.py/pull/3875
- - https://github.com/ethereum/web3.py/security/advisories/GHSA-5hr4-253g-cpx2
- - https://www.vulncheck.com/advisories/web3-py-7.15.0-through-7.16.0-and-8.0-0b2-through-8.0.0-ccip-read-ssrf-bypass

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