CVE-2026-22866

Description

### 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

How to fix CVE-2026-22866

No fixed version has been published yet. Mitigate by removing the affected package or applying upstream guidance from the references below.

—no fix listed

Is CVE-2026-22866 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

from 0, <= 1.6.2

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 4.0	—	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