What is CVE-2021-34371?

CVE-2021-34371 is a critical-severity vulnerability in Neo4j, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-08-05.

How severe is CVE-2021-34371?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2021-34371 known to be exploited?

15 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Deserialization in Neo4j

CVE-2021-34371

Neo4j through 3.4.18 (with the shell server enabled) exposes an RMI service that arbitrarily deserializes Java objects, e.g., through setSessionVariable. An attacker can abuse this for remote code execution because there are dependencies with exploitable gadget chains.

Vulnerability class: Insecure Deserialization

Published 2021-08-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.134 (96.3th percentile), scored 2026-09-30.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 96th percentile — 96.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.134 · newest: 0.134 · change: 0.000

Affected products

Neo4j

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

Public proof-of-concept exploits

References

www.exploit-db.com/exploits/50170 (Exploit, VDB Entry, Third Party Advisory)

Frequently asked questions

What is CVE-2021-34371?: CVE-2021-34371 is a critical-severity vulnerability in Neo4j, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-08-05.
How severe is CVE-2021-34371?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-34371 known to be exploited?: 15 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.