Is CVE-2016-5261 in the CISA KEV catalog?

No. CVE-2016-5261 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2016-5261?

CVE-2016-5261 has a CVSS v3 base score of 8.8 (HIGH).

What is the EPSS score for CVE-2016-5261?

CVE-2016-5261 has an EPSS score of 4.18% (90th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2016-5261?

Upgrade firefox on debian unstable to 48.0-1 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2016-5261

HIGHEPSS 90th pctl

8.8

CVSS v3

NVD

Description

Integer overflow in the WebSocketChannel class in the WebSockets subsystem in Mozilla Firefox before 48.0 and Firefox ESR < 45.4 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption) via crafted packets that trigger incorrect buffer-resize operations during buffering.

CWE-190Integer Overflow

How to fix

Remediation Available

firefoxDebian

Fixed in:48.0-1CVE-2016-5261

firefoxUbuntu

Fixed in:48.0+build2-0ubuntu0.14.04.1USN-3044-1

Fixed in:48.0+build2-0ubuntu0.16.04.1USN-3044-1

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

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploit Intelligence

4.18%probability of exploitation in 30 days

90thpercentile

Elevated risk: more likely to be exploited than 90% of all known CVEs.

References

Vendor Advisory1

mozilla.org

Issue Tracking1

bugzilla.mozilla.org

Other references10

Related Vulnerabilities

Other CWE-190 (Integer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-16040	Medium	6.5	100%	-	Fix
CVE-2019-11477	High	7.5	99%	-	Fix
CVE-2023-44443	High	7.8	94%	-	Fix
CVE-2014-0569	High	9.3	90%	-	-
CVE-2017-3599	High	7.5	90%	-	Fix
CVE-2023-21716	Critical	9.8	82%	-	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 2026-05-06.