CVE-2026-22866: ENS DNSSEC Oracle Vulnerable to RSA Signature Forgery via Missing PKCS#1 v1.5 Padding Validation
(updated )
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.
Affected contracts
| Contract | Address | Status |
|---|---|---|
| RSASHA256Algorithm | 0x9D1B5a639597f558bC37Cf81813724076c5C1e96 | Vulnerable |
| RSASHA1Algorithm | 0x6ca8624Bc207F043D140125486De0f7E624e37A1 | Vulnerable |
| DNSSECImpl | 0x0fc3152971714E5ed7723FAFa650F86A4BaF30C5 | Uses vulnerable algorithms |
| DNSRegistrar | 0xB32cB5677a7C971689228EC835800432B339bA2B | Attack entry point |
References
- github.com/advisories/GHSA-c6rr-7pmc-73wc
- github.com/ensdomains/ens-contracts
- github.com/ensdomains/ens-contracts-bug-62248-pr-509
- github.com/ensdomains/ens-contracts/commit/c76c5ad0dc9de1c966443bd946fafc6351f87587
- github.com/ensdomains/ens-contracts/security/advisories/GHSA-c6rr-7pmc-73wc
- nvd.nist.gov/vuln/detail/CVE-2026-22866
Code Behaviors & Features
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