CVE-2020-28928: In musl libc through 1.2.1, wcsnrtombs mishandles particular combinations of destination buffer size and sourc

Routine

MEDIUM 5.5WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2020-28928 is a medium-severity flaw (CVSS 5.5) affecting musl, debian linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In musl libc through 1.2.1, wcsnrtombs mishandles particular combinations of destination buffer size and source character limit, as demonstrated by an invalid write access (buffer overflow).

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.7% (top 49%)
CISA exploited list	No
Weakness	CWE-787
Published	2020-11-24
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · fedoraproject · musl-libc · oracle

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-11-24 18:15 UTCPublished CVE record published
2026-06-17 03:10 UTCUpdated Record last modified

musl-libc musl UPGRADE

Affected: <= 1.2.1

Fixed in: newer than 1.2.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy musl || rpm -q musl || musl --version

2. UPGRADE to newer than 1.2.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade musl

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade musl

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

debian debian linux MITIGATE

Affected: 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

fedoraproject fedora MITIGATE

Affected: 33 · 34

Fixed in: no fixed release known

Safe to downgrade to: a release before 33

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

oracle graalvm DOWNGRADE

Affected: 20.3.2 · 21.1.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 20.3.2

1. Check installed version

apt-cache policy graalvm || rpm -q graalvm || graalvm --version

2. No fixed release: DOWNGRADE to a release before 20.3.2 (Debian / Ubuntu)

apt-cache madison graalvm sudo apt install graalvm=<VERSION_BEFORE_20.3.2> sudo apt-mark hold graalvm

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list graalvm sudo dnf downgrade graalvm-<VERSION_BEFORE_20.3.2> sudo dnf versionlock add graalvm

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-28928?

musl: upgrade to newer than 1.2.1; debian linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-28928 being exploited?

CVE-2020-28928 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-28928 affect?

CVE-2020-28928 affects musl, debian linux, fedora. Severity is medium (CVSS 5.5). In musl libc through 1.2.1, wcsnrtombs mishandles particular combinations of destination buffer size and source character limit, as demonstrated by an invalid write access (buffer overflow).

How urgent is CVE-2020-28928?

Priority 37/100. On your watchlist

Software pages

Debian vulnerabilities

Related CVEs

CVE-2025-26519 HIGH 8.1 UPGRADE musl libc 0.9.13 through 1.2.5 before 1.2.6 has an out-of-bounds write vulnerability when an attacker can trig
CVE-2019-14697 CRITICAL 9.8 UPGRADE musl libc through 1.1.23 has an x87 floating-point stack adjustment imbalance, related to the math/i386/ direc
CVE-2017-15650 HIGH 7.5 UPGRADE musl libc before 1.1.17 has a buffer overflow via crafted DNS replies because dns_parse_callback in network/lo
CVE-2016-8859 CRITICAL 9.8 UPGRADE Multiple integer overflows in the TRE library and musl libc allow attackers to cause memory corruption via a l
CVE-2015-1817 CRITICAL 9.8 DOWNGRADE Stack-based buffer overflow in the inet_pton function in network/inet_pton.c in musl libc 0.9.15 through 1.0.4

References

← Back to latest CVEs