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.

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.

Published 2026-02-25 · last modified 2026-06-17.

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.

EPSS exploit prediction

EPSS: 0.002 (6.8th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 6.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Ens.domains Ethereum Name Service
Ensdomains Ens-Contracts — versions <= 1.6.2

Weakness classification (CWE)

CWE-347 — Improper Verification of Cryptographic Signature

References

github.com/ensdomains/ens-contracts/security/advisories/GHSA-c6rr-7pmc-73wc (Patch, Vendor Advisory)
github.com/ensdomains/ens-contracts/commit/c76c5ad0dc9de1c966443bd946fafc6351f8… (Patch)
github.com/ensdomains/ens-contracts-bug-62248-pr-509 (Patch, 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.