Is CVE-2013-4421 in the CISA KEV catalog?

No. CVE-2013-4421 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2013-4421?

CVE-2013-4421 has a CVSS v2 base score of 5.0 (MEDIUM).

What is the EPSS score for CVE-2013-4421?

CVE-2013-4421 has an EPSS score of 6.42% (93th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2013-4421?

Upgrade dropbear on debian 11 to 2012.55-1.4 or later.

CVE & CISA-KEV Catalog

CVE-2013-4421

MEDIUMEPSS 93th pctl

5.0

CVSS v2

NVD

Description

The buf_decompress function in packet.c in Dropbear SSH Server before 2013.59 allows remote attackers to cause a denial of service (memory consumption) via a compressed packet that has a large size when it is decompressed.

CWE-189

How to fix

Remediation Available

dropbearDebian

Fixed in:2012.55-1.4CVE-2013-4421

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v2 Vector

No CVSS vector data available.

Exploit Intelligence

6.42%probability of exploitation in 30 days

93rdpercentile

High risk: more likely to be exploited than 93% of all known CVEs.

References

Patch1

secure.ucc.asn.au

Vendor Advisory1

matt.ucc.asn.au

Third-Party Advisory8

Related Vulnerabilities

Other CWE-189 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2015-1538	High	10.0	99%	-	-
CVE-2006-3747	High	7.6	96%	-	Fix
CVE-2007-0071	High	9.3	93%	-	-
CVE-2015-3829	High	10.0	90%	-	-
CVE-2015-3864	High	10.0	87%	-	-
CVE-2015-1539	High	10.0	86%	-	-

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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 2026-04-29.