Is CVE-2026-21920 in the CISA KEV catalog?

No. CVE-2026-21920 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-21920?

CVE-2026-21920 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2026-21920?

CVE-2026-21920 has an EPSS score of 0.44% (36th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix or mitigate CVE-2026-21920?

No published fix for CVE-2026-21920 has been found yet. Check the linked vendor advisories for guidance as it becomes available.

CVE & CISA-KEV Catalog

CVE-2026-21920

HIGH

7.5

CVSS v3

NVD

Description

An Unchecked Return Value vulnerability in the DNS module of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). If an SRX Series device configured for DNS processing, receives a specifically formatted DNS request flowd will crash and restart, which causes a service interruption until the process has recovered. This issue affects Junos OS on SRX Series: * 23.4 versions before 23.4R2-S5, * 24.2 versions before 24.2R2-S1, * 24.4 versions before 24.4R2. This issue does not affect Junos OS versions before 23.4R1.

CWE-252

How to fix

No published remediation has been found for this vulnerability's affected products yet.

Mitigation guidance may be in the linked vendor advisories in the References section below.

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CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploit Intelligence

0.44%probability of exploitation in 30 days

36thpercentile

Low risk: more likely to be exploited than 36% of all known CVEs.

References

Vendor Advisory2

Related Vulnerabilities

Other CWE-252 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2005-4360	High	7.8	87%	-	-
CVE-2007-3798	Critical	9.8	70%	-	Fix
CVE-2010-0211	Critical	9.8	29%	-	Fix
CVE-2022-23626	High	8.5	9.9%	-	Fix
CVE-2019-10902	High	7.5	4.7%	-	-
CVE-2018-20216	High	7.5	3.9%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-01-23.