CVE-2021-3518: There's a flaw in libxml2 in versions before 2.9.11

Q: How do I fix CVE-2021-3518?

libxml2: upgrade to 2.9.11; debian linux: mitigate or apply the listed mitigation; jboss core services: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-3518 being exploited?

CVE-2021-3518 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-2021-3518 affect?

CVE-2021-3518 affects libxml2, debian linux, jboss core services. Severity is high (CVSS 8.8). There's a flaw in libxml2 in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by an application linked with libxml2 could trigger a use-after-free. The greatest impact from this flaw is to confidentia

Q: How urgent is CVE-2021-3518?

Priority 60/100. High severity; EPSS top 2%: very likely to be exploited; On your watchlist

This week

HIGH 8.8WATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-3518 is a high-severity flaw (CVSS 8.8) affecting libxml2, debian linux, jboss core services. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

There's a flaw in libxml2 in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by an application linked with libxml2 could trigger a use-after-free. The greatest impact from this flaw is to confidentiality, integrity, and availability.

Why this priority

High severity
EPSS top 2%: very likely to be exploited
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	21.9% (top 2%)
CISA exploited list	No
Weakness	CWE-416
Published	2021-05-18
Last modified	2026-10-14

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

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

Am I affected?

Timeline

2021-05-18 12:15 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.

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.

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.

redhat enterprise linux MITIGATE

Affected: 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

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.

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.

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-2021-3518?

libxml2: upgrade to 2.9.11; debian linux: mitigate or apply the listed mitigation; jboss core services: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-3518 being exploited?

CVE-2021-3518 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-2021-3518 affect?

CVE-2021-3518 affects libxml2, debian linux, jboss core services. Severity is high (CVSS 8.8). There's a flaw in libxml2 in versions before 2.9.11. An attacker who is able to submit a crafted file to be processed by an application linked with libxml2 could trigger a use-after-free. The greatest impact from this flaw is to confidentia

How urgent is CVE-2021-3518?

Priority 60/100. High severity; EPSS top 2%: very likely to be exploited; On your watchlist

Software pages

Debian vulnerabilities · JBoss and WildFly vulnerabilities · libxml2 vulnerabilities

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References

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