CVE-2021-34433

In Eclipse Californium version 2.0.0 to 2.6.4 and 3.0.0-M1 to 3.0.0-M3, the certificate based (x509 and RPK) DTLS handshakes accidentally succeeds without verifying the server side's signature on the client side, if that signature is not included in the server's ServerKeyExchange.

Published: 2021-08-20 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-34433 is rated Low Risk (39.2/100): CVSS High severity, with low exploitation likelihood (EPSS 0.34%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-34433

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.05% 0.34% +0.29%
2 2025-03-30 0.06% 0.05% -0.01%
3 2025-03-29 — 0.06% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-34433

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-34433

Affected software / configurations for CVE-2021-34433

Vendor Product Version Raw CPE
eclipse californium >= 2.0.0, < 2.6.5 cpe:2.3:a:eclipse:californium:*:*:*:*:*:*:*:*
eclipse californium 3.0.0 cpe:2.3:a:eclipse:californium:3.0.0:m1:*:*:*:*:*:*
eclipse californium 3.0.0 cpe:2.3:a:eclipse:californium:3.0.0:m2:*:*:*:*:*:*
eclipse californium 3.0.0 cpe:2.3:a:eclipse:californium:3.0.0:m3:*:*:*:*:*:*

References for CVE-2021-34433

URL Tags
https://bugs.eclipse.org/bugs/show_bug.cgi?id=575281 Issue Tracking Vendor Advisory
cvelogic Threat Intelligence