ENS DNSSEC Oracle Vulnerable to RSA Signature Forgery via Missing PKCS#1 v1.5 Padding Validation
Impact
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 |
Patches
The bug was reported via Immunefi with possible solutions. The patch was merged at https://github.com/ensdomains/ens-contracts/commit/c76c5ad0dc9de1c966443bd946fafc6351f87587
Workarounds
- Deploy the patched contracts
- Point DNSSECImpl.setAlgorithm to the deployed contract
Resources
https://github.com/ensdomains/ens-contracts-bug-62248-pr-509
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | @ensdomains/ens-contracts | <= 1.6.2 | no fix |
References
- https://github.com/ensdomains/ens-contracts/security/advisories/GHSA-c6rr-7pmc-73wc
- https://nvd.nist.gov/vuln/detail/CVE-2026-22866
- https://github.com/ensdomains/ens-contracts/commit/c76c5ad0dc9de1c966443bd946fafc6351f87587
- https://github.com/ensdomains/ens-contracts
- https://github.com/ensdomains/ens-contracts-bug-62248-pr-509
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U- Weakness (CWE)
CWE-347- Platform
- npm
- Package
@ensdomains/ens-contracts- Disclosed
- 25.02.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-c6rr-7pmc-73wc - CC BY 4.0
Vulnerability history: @ensdomains/ens-contracts
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 08.2023 02.2026
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- Medium 1
- Low 1
Disclosures per year
- 2023: 1
- 2024: 0
- 2025: 0
- 2026: 1
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