CVE-2021-3541: A flaw was found in libxml2

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MEDIUM 6.5WATCHLISTUPGRADEMITIGATEDOWNGRADE

CVE-2021-3541 is a medium-severity flaw (CVSS 6.5) affecting libxml2, jboss core services, zfs storage appliance kit. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in libxml2. Exponential entity expansion attack its possible bypassing all existing protection mechanisms and leading to denial of service.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	2.1% (top 19%)
CISA exploited list	No
Weakness	CWE-776
Published	2021-07-09
Last modified	2026-10-14

Publisher (CNA): Red Hat, Inc. · Vendor: netapp · oracle · redhat · xmlsoft

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

Am I affected?

Timeline

2021-07-09 17:15 UTCPublished CVE record published
2026-10-14 10:17 UTCUpdated Record last modified

xmlsoft libxml2 UPGRADE

Affected: < 2.9.11

Fixed in: 2.9.11

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libxml2 || rpm -q libxml2 || libxml2 --version

2. UPGRADE to 2.9.11 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libxml2

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libxml2

Note

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

redhat jboss core services 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 jboss-core-services || rpm -q jboss-core-services || jboss-core-services --version

No fixed or unaffected release known

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

oracle zfs storage appliance kit DOWNGRADE

Affected: 8.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.8

1. Check installed version

apt-cache policy zfs-storage-appliance-kit || rpm -q zfs-storage-appliance-kit || zfs-storage-appliance-kit --version

2. No fixed release: DOWNGRADE to a release before 8.8 (Debian / Ubuntu)

apt-cache madison zfs-storage-appliance-kit sudo apt install zfs-storage-appliance-kit=<VERSION_BEFORE_8.8> sudo apt-mark hold zfs-storage-appliance-kit

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

dnf --showduplicates list zfs-storage-appliance-kit sudo dnf downgrade zfs-storage-appliance-kit-<VERSION_BEFORE_8.8> sudo dnf versionlock add zfs-storage-appliance-kit

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.

netapp active iq unified manager 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 active-iq-unified-manager || rpm -q active-iq-unified-manager || active-iq-unified-manager --version

No fixed or unaffected release known

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

netapp cloud backup 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 cloud-backup || rpm -q cloud-backup || cloud-backup --version

No fixed or unaffected release known

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

netapp clustered data ontap 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 clustered-data-ontap || rpm -q clustered-data-ontap || clustered-data-ontap --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-2021-3541?

libxml2: upgrade to 2.9.11; jboss core services: mitigate or apply the listed mitigation; zfs storage appliance kit: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-3541 being exploited?

CVE-2021-3541 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-2021-3541 affect?

CVE-2021-3541 affects libxml2, jboss core services, zfs storage appliance kit. Severity is medium (CVSS 6.5). A flaw was found in libxml2. Exponential entity expansion attack its possible bypassing all existing protection mechanisms and leading to denial of service.

How urgent is CVE-2021-3541?

Priority 48/100. On your watchlist

Software pages

JBoss and WildFly vulnerabilities · libxml2 vulnerabilities

Related CVEs

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CVE-2026-11979 HIGH 7.8 UPGRADE libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --she
CVE-2025-9714 MEDIUM 6.2 UPGRADE Uncontrolled recursion in XPath evaluation in libxml2 up to and including version 2.9.14 allows a local attack

References

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