Vulnerability in Ens.domains Ethereum Name Service
CVE-2026-22866
Ethereum Name Service (ENS) is a distributed, open, and extensible naming system based on the Ethereum blockchain. In versions 1.6.2 and prior, the `RSASHA256Algorithm` and `RSASHA1Algorithm` contracts fail to validate PKCS#1 v1.5 padding structure when verifying RSA signatures. The contracts only check if the last 32 (or 20) bytes of the decrypted signature match the expected hash. This enables Bleichenbacher's 2006 signature forgery attack against DNS zones using RSA keys with low public exponents (e=3). Two ENS-supported TLDs (.cc and .name) use e=3 for their Key Signing Keys, allowing any domain under these TLDs to be fraudulently claimed on ENS without DNS ownership. Apatch was merged at commit c76c5ad0dc9de1c966443bd946fafc6351f87587. Possible workarounds include deploying the patched contracts and pointing DNSSECImpl.setAlgorithm to the deployed contract.
EPSS: 0.002 (7.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
Affected products
- Ens.domains Ethereum_name_service
- Ensdomains Ens-contracts — versions <= 1.6.2
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (Patch, x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-22866?
- CVE-2026-22866 is a high-severity vulnerability in Ens.domains Ethereum Name Service, classified under Improper Verification of Cryptographic Signature. CVSS score: 7.5/10. Published 2026-02-25.
- How severe is CVE-2026-22866?
- High severity. CVSS v3 base score is 7.5 out of 10.