Is CVE-2021-4156 in the CISA KEV catalog?

No. CVE-2021-4156 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-4156?

CVE-2021-4156 has a CVSS v3 base score of 7.1 (HIGH).

What is the EPSS score for CVE-2021-4156?

CVE-2021-4156 has an EPSS score of 1.75% (75th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-4156?

Upgrade libsndfile on debian 11 to 1.0.31-2+deb11u2 or later. Fixes are available for 5 affected products.

CVE & CISA-KEV Catalog

CVE-2021-4156

HIGHEPSS 75th pctl

7.1

CVSS v3

NVD

Description

An out-of-bounds read flaw was found in libsndfile's FLAC codec functionality. An attacker who is able to submit a specially crafted file (via tricking a user to open or otherwise) to an application linked with libsndfile and using the FLAC codec, could trigger an out-of-bounds read that would most likely cause a crash but could potentially leak memory information that could be used in further exploitation of other flaws.

CWE-125Out-of-bounds Read

How to fix

Remediation Available

libsndfileDebian

Fixed in:1.0.31-2+deb11u2CVE-2021-4156

Fixed in:1.1.0-1CVE-2021-4156

libsndfileUbuntu

Fixed in:1.0.25-7ubuntu2.2+esm4USN-7273-1

Fixed in:1.0.25-10ubuntu0.16.04.3+esm2USN-5409-1

Fixed in:1.0.28-4ubuntu0.18.04.2+esm2USN-7273-1

Fixed in:1.0.28-7ubuntu0.3USN-7273-1

Fixed in:1.0.31-2ubuntu0.2USN-7273-1

libsndfile1Ubuntu

Fixed in:1.0.25-7ubuntu2.2+esm4USN-7273-1

Fixed in:1.0.25-10ubuntu0.16.04.3+esm2USN-5409-1

Fixed in:1.0.28-4ubuntu0.18.04.2+esm2USN-7273-1

Fixed in:1.0.28-7ubuntu0.3USN-7273-1

Fixed in:1.0.31-2ubuntu0.2USN-7273-1

libsndfile1-devUbuntu

Fixed in:1.0.25-10ubuntu0.16.04.3+esm2USN-5409-1

sndfile-programsUbuntu

Fixed in:1.0.25-7ubuntu2.2+esm4USN-7273-1

Fixed in:1.0.25-10ubuntu0.16.04.3+esm2USN-5409-1

Fixed in:1.0.28-4ubuntu0.18.04.2+esm2USN-7273-1

Fixed in:1.0.28-7ubuntu0.3USN-7273-1

Fixed in:1.0.31-2ubuntu0.2USN-7273-1

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

ConfidentialityLow

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

1.75%probability of exploitation in 30 days

75thpercentile

Elevated risk: more likely to be exploited than 75% of all known CVEs.

References

Patch1

github.com

Exploit2

Third-Party Advisory2

Other references2

Related Vulnerabilities

Other CWE-125 (Out-of-bounds Read) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2014-0160	High	7.5	100%	KEV	Fix
CVE-2025-5777	High	7.5	100%	KEV + Ransom	Fix
CVE-2021-4034	High	7.8	95%	KEV	Fix
CVE-2023-21769	High	7.5	92%	-	Fix
CVE-2023-49285	High	8.6	89%	-	Fix
CVE-2020-8794	Critical	9.8	89%	-	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 2025-12-11.