CVE-2026-22866 ENS DNSSEC Oracle Vulnerable to RSA Signature Forgery via Missing PKCS#1 v1.5 Padding Validation
Attackers can forge RSA signatures to fraudulently claim domains under specific TLDs due to missing PKCS#1 v1.5 padding validation in ENS contracts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-22866?
CVE-2026-22866 is a low-severity vulnerability in ensdomains ens-contracts, published on 25 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-347
Which versions are affected by CVE-2026-22866?
2 open source packages ship an affected version, including @ensdomains/ens-contracts. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@ensdomains/ens-contracts npm | All versions to 1.6.2 | None |
@ensdomains/ens-contracts npm | All versions to 1.6.2 | None |
Products include Ens.domains Ethereum Name Service.
How do I fix CVE-2026-22866?
No fix has been published for CVE-2026-22866 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-22866 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-22866 exists.
Other vulnerabilities in ensdomains ens-contracts
Sources
Also known as GHSA-c6rr-7pmc-73wc.