How severe is CVE-2026-22866?

No CVSS score has been assigned to CVE-2026-22866 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-22866?

CVE-2026-22866 affects the following packages: @ensdomains/ens-contracts (npm). Ecosystems affected: npm.

How do I fix CVE-2026-22866?

The records we use list no patched version of @ensdomains/ens-contracts for CVE-2026-22866. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.

How do I detect CVE-2026-22866 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @ensdomains/ens-contracts, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-22866 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-22866 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-22866 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-22866?

CVE-2026-22866 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 10th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-22866?

CVE-2026-22866 is classified as CWE-347 (CWE-347). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-22866 published, and has it been updated?

CVE-2026-22866 was published on February 25, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-22866 — @ensdomains/ens-contracts

Fix: ensdomains/ens-contracts@c76c5ad

CVE-2026-22866 is a CWE-347 vulnerability in @ensdomains/ens-contracts. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.

ENS DNSSEC Oracle Vulnerable to RSA Signature Forgery via Missing PKCS#1 v1.5 Padding Validation

Also known asGHSA-c6rr-7pmc-73wc

Published

Feb 25, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

See advisory

Exploits

None indexed

Exploitation data as of Oct 24, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk+0.02%

Lower risk than most CVEs10th percentile — riskier than 10% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

81other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@ensdomains/ens-contractsnpm

1Kdownloads / week

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

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@ensdomains/ens-contracts`	all versions	No fix

Affected Products

1 product · 1 configurations

Application

ethereum name serviceens.domains

≤ 1.6.2

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @ensdomains/ens-contracts, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
The records we use list no patched version of @ensdomains/ens-contracts for CVE-2026-22866. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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 --

O3 Security · Impact-Aware SCA

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