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Fencer Vulns
medium 6.5

CVE-2021-21369 json

Potential DoS in Besu HTTP JSON-RPC API

published 2021-03-09 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-8681

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 76%
public exploits
0
none known

Summary

Hyperledger Besu is an open-source, MainNet compatible, Ethereum client written in Java. In Besu before version 1.5.1 there is a denial-of-service vulnerability involving the HTTP JSON-RPC API service. If username and password authentication is enabled for the HTTP JSON-RPC API service, then prior to making any requests to an API endpoint the requestor must use the login endpoint to obtain a JSON web token (JWT) using their credentials. A single user can readily overload the login endpoint with invalid requests (incorrect password). As the supplied password is checked for validity on the main vertx event loop and takes a relatively long time this can cause the processing of other valid requests to fail. A valid username is required for this vulnerability to be exposed. This has been fixed in version 1.5.1.

Patch / fix

  • linuxfoundation besu 1.5.1

Exploit prediction

1.67% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 4.0 AV:N/AC:L/Au:S/C:N/I:N/A:P

Affected products

  • hyperledger besu

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.