CVE-2021-33910: basic/unit-name.c in systemd prior to 246.15, 247.8, 248.5, and 249.1 has a Memory Allocation with an Excessiv

Q: How do I fix CVE-2021-33910?

systemd: upgrade to 246.15, 247.8, 248.5, 249.1; fedora: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-33910 being exploited?

CVE-2021-33910 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-33910 affect?

CVE-2021-33910 affects systemd, fedora, debian linux. Severity is medium (CVSS 5.5). basic/unit-name.c in systemd prior to 246.15, 247.8, 248.5, and 249.1 has a Memory Allocation with an Excessive Size Value (involving strdupa and alloca for a pathname controlled by a local attacker) that results in an operating system cras

Q: How urgent is CVE-2021-33910?

Priority 53/100. EPSS top 5%: very likely to be exploited; Public exploit reference; On your watchlist

This week

MEDIUM 5.5WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-33910 is a medium-severity flaw (CVSS 5.5) affecting systemd, fedora, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

basic/unit-name.c in systemd prior to 246.15, 247.8, 248.5, and 249.1 has a Memory Allocation with an Excessive Size Value (involving strdupa and alloca for a pathname controlled by a local attacker) that results in an operating system crash.

Why this priority

EPSS top 5%: very likely to be exploited
Public exploit reference
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	8.8% (top 5%)
CISA exploited list	No
Weakness	CWE-770
Published	2021-07-20
Last modified	2026-10-14

Publisher (CNA): MITRE · Vendor: debian · fedoraproject · netapp · systemd project

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-07-20 19:15 UTCPublished CVE record published
2026-10-14 12:17 UTCUpdated Record last modified

systemd project systemd UPGRADE

Affected: < 246.15 · >= 247 and < 247.8 · >= 248 and < 248.5 · >= 249 and < 249.1

Fixed in: 246.15, 247.8, 248.5, 249.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 246.15 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade systemd

Note

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

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.

debian debian linux MITIGATE

Affected: 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.0

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.

netapp hci management node MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy hci-management-node || rpm -q hci-management-node || hci-management-node --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp solidfire MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

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

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

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-2021-33910?

systemd: upgrade to 246.15, 247.8, 248.5, 249.1; fedora: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-33910 being exploited?

CVE-2021-33910 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-2021-33910 affect?

CVE-2021-33910 affects systemd, fedora, debian linux. Severity is medium (CVSS 5.5). basic/unit-name.c in systemd prior to 246.15, 247.8, 248.5, and 249.1 has a Memory Allocation with an Excessive Size Value (involving strdupa and alloca for a pathname controlled by a local attacker) that results in an operating system cras

How urgent is CVE-2021-33910?

Priority 53/100. EPSS top 5%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

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References

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