Is CVE-2016-5270 in the CISA KEV catalog?

No. CVE-2016-5270 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2016-5270?

CVE-2016-5270 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2016-5270?

CVE-2016-5270 has an EPSS score of 3.93% (89th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2016-5270?

Upgrade firefox on debian unstable to 49.0-1 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2016-5270

CRITICALEPSS 89th pctl

9.8

CVSS v3

NVD

Description

Heap-based buffer overflow in the nsCaseTransformTextRunFactory::TransformString function in Mozilla Firefox before 49.0, Firefox ESR 45.x before 45.4, and Thunderbird < 45.4 allows remote attackers to cause a denial of service (boolean out-of-bounds write) or possibly have unspecified other impact via Unicode characters that are mishandled during text conversion.

CWE-119Buffer Overflow CWE-787Out-of-bounds Write

How to fix

Remediation Available

firefoxDebian

Fixed in:49.0-1CVE-2016-5270

firefoxUbuntu

Fixed in:49.0+build4-0ubuntu0.14.04.1USN-3076-1

Fixed in:49.0+build4-0ubuntu0.16.04.1USN-3076-1

thunderbirdUbuntu

Fixed in:1:45.4.0+build1-0ubuntu0.14.04.1USN-3112-1

Fixed in:1:45.4.0+build1-0ubuntu0.16.04.1USN-3112-1

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 InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

3.93%probability of exploitation in 30 days

89thpercentile

Elevated risk: more likely to be exploited than 89% of all known CVEs.

References

Vendor Advisory1

mozilla.org

Issue Tracking1

bugzilla.mozilla.org

Other references8

Related Vulnerabilities

Other CWE-119 (Buffer Overflow) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-4966	Critical	9.4	100%	KEV + Ransom	Fix
CVE-2017-11882	High	7.8	100%	KEV + Ransom	-
CVE-2020-0796	Critical	10.0	100%	KEV + Ransom	-
CVE-2008-4250	Critical	9.8	99%	KEV	-
CVE-2017-15944	Critical	9.8	98%	KEV	Fix
CVE-2015-0014	High	10.0	97%	-	-

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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.