CVE-2026-40094

CVE-2026-40094 is a medium-severity vulnerability with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-754.

Key facts

Description

nimiq-blockchain provides persistent block storage for Nimiq's Rust implementation. In versions 1.3.0 and prior, network-libp2p discovery accepts signed PeerContact updates from untrusted peers and stores them in a peer contact book, eventually leading to address book crash. A PeerContact can legally contain an empty addresses list (no intrinsic validation enforces non-empty). Later, PeerContactBook::known_peers builds an address book by taking addresses.first().expect("every peer should have at least one address"). If the attacker has inserted a signed peer contact with addresses=[], any call to get_address_book (RPC/web client) can panic and crash the node/RPC task depending on panic settings. This issue has been fixed in version 1.4.0.

Frequently asked questions

What is CVE-2026-40094?
nimiq-blockchain provides persistent block storage for Nimiq's Rust implementation. In versions 1.3.0 and prior, network-libp2p discovery accepts signed PeerContact updates from untrusted peers and stores them in a peer contact book, eventually leading to address book crash. A PeerContact can legally contain an empty addresses list (no intrinsic validation enforces non-empty). Later, PeerContactBook::known_peers builds an address book by taking addresses.first().expect("every peer should have at least one address"). If the attacker has inserted a signed peer contact with addresses=[], any call to get_address_book (RPC/web client) can panic and crash the node/RPC task depending on panic settings. This issue has been fixed in version 1.4.0.
How severe is CVE-2026-40094?
CVE-2026-40094 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-40094 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-40094?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-40094 have an EU (EUVD) identifier?
Yes. CVE-2026-40094 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-31195.
When was CVE-2026-40094 published?
CVE-2026-40094 was published on 2026-05-20 and last updated on 2026-06-17.

References

Other CWE-754 (Improper Check for Unusual or Exceptional Conditions) vulnerabilities

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