Skip to content
Noroxi
CVE-2021-3541· NVD / CVE Program· CNA redhat

A flaw was found in libxml2.

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 2% (FIRST EPSS); higher than 81.2% of all records.
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: libxml2-devel (AlmaLinux:8) 2.9.7-9.el8_4.2; libxml2 (Alpine:v3.11) 2.9.12-r0; libxml2 (Alpine:v3.13) 2.9.11-r0.
  • Mentioned 6 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to libxml2-devel (AlmaLinux:8) 2.9.7-9.el8_4.2; libxml2 (Alpine:v3.11) 2.9.12-r0; libxml2 (Alpine:v3.13) 2.9.11-r0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Jul 9, 2021
Updated
Oct 14, 2026
EPSS
2.0% · 81th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
1 / 30 · 2.0%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-3541

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for xmlsoft records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
xmlsoftlibxml2
redhatjboss core services
oraclezfs storage appliance kit
netappactive iq unified manager
netappcloud backup
netappclustered data ontap
netappclustered data ontap antivirus connector
netappmanageability software development kit
netappontap select deploy administration utility
netappsmi-s provider
netappsnapdrive
netapph410c firmware

and 15 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • netapp active iq unified managerall versions
  • netapp cloud backupall versions
  • netapp clustered data ontapall versions
  • netapp clustered data ontap antivirus connectorall versions
  • netapp h300e firmwareall versions
  • netapp h300s firmwareall versions
  • netapp h410c firmwareall versions
  • netapp h410s firmwareall versions
  • netapp h500e firmwareall versions
  • netapp h500s firmwareall versions
  • netapp h700e firmwareall versions
  • netapp h700s firmwareall versions
  • netapp manageability software development kitall versions
  • netapp ontap select deploy administration utilityall versions
  • netapp smi-s providerall versions
  • netapp snapdriveall versions
  • oracle zfs storage appliance kit8.8
  • redhat jboss core servicesall versions
  • xmlsoft libxml2before 2.9.11

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a libxml2

    • 2.9.11affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8libxml2-develbefore 2.9.7-9.el8_4.22.9.7-9.el8_4.2
Alpine:v3.11libxml2before 2.9.12-r02.9.12-r0
Alpine:v3.13libxml2before 2.9.11-r02.9.11-r0
Debian:12libxml2before 2.9.10+dfsg-6.72.9.10+dfsg-6.7
Debian:9libxml2before 2.9.4+dfsg1-2.2+deb9u52.9.4+dfsg1-2.2+deb9u5
openSUSE:Leap 15.2libxml2before 2.9.7-lp152.10.15.12.9.7-lp152.10.15.1
openSUSE:Leap 15.2python-libxml2-pythonbefore 2.9.7-lp152.10.15.12.9.7-lp152.10.15.1
openSUSE:Leap 15.3libxml2before 2.9.7-3.37.12.9.7-3.37.1
openSUSE:Leap 15.3python-libxml2-pythonbefore 2.9.7-3.37.12.9.7-3.37.1
openSUSE:Leap 15.4python-libxml2-pythonbefore 2.9.7-150000.3.57.12.9.7-150000.3.57.1
openSUSE:Tumbleweedlibxml2before 2.9.12-1.22.9.12-1.2
Red Hat:enterprise_linux:8::appstreamlibxml2-debuginfobefore 0:2.9.7-9.el8_4.20:2.9.7-9.el8_4.2
Red Hat:enterprise_linux:8::appstreamlibxml2-debugsourcebefore 0:2.9.7-9.el8_4.20:2.9.7-9.el8_4.2
Red Hat:enterprise_linux:8::appstreamlibxml2-develbefore 0:2.9.7-9.el8_4.20:2.9.7-9.el8_4.2
Red Hat:enterprise_linux:8::appstreampython3-libxml2-debuginfobefore 0:2.9.7-9.el8_4.20:2.9.7-9.el8_4.2
Red Hat:enterprise_linux:8::baseoslibxml2before 0:2.9.7-9.el8_4.20:2.9.7-9.el8_4.2
Red Hat:enterprise_linux:8::baseospython3-libxml2before 0:2.9.7-9.el8_4.20:2.9.7-9.el8_4.2
Red Hat:jboss_core_services:1::el7jbcs-httpd24-apr-utilbefore 0:1.6.1-91.jbcs.el70:1.6.1-91.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-apr-util-debuginfobefore 0:1.6.1-91.jbcs.el70:1.6.1-91.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-apr-util-develbefore 0:1.6.1-91.jbcs.el70:1.6.1-91.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-apr-util-ldapbefore 0:1.6.1-91.jbcs.el70:1.6.1-91.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-apr-util-mysqlbefore 0:1.6.1-91.jbcs.el70:1.6.1-91.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-apr-util-nssbefore 0:1.6.1-91.jbcs.el70:1.6.1-91.jbcs.el7
Red Hat:jboss_core_services:1::el7jbcs-httpd24-apr-util-odbcbefore 0:1.6.1-91.jbcs.el70:1.6.1-91.jbcs.el7

+96

Same product

xmlsoft: all records

Other highest-scoring records for the same primary product.

  • CVE-2008-3529Heap-based buffer overflow in the xmlParseAttValueComplex function in parser.c in libxml2 before 2.7.0 allows context-dependent attackers to
    47Plan
  • CVE-2017-7376Buffer overflow in libxml2 allows remote attackers to execute arbitrary code by leveraging an incorrect limit for port values when handling
    46Plan
  • CVE-2022-40303An issue was discovered in libxml2 before 2.10.3.
    42Plan

Published before and after this one in the same product

  • ← EarlierCVE-2021-3518May 18, 2021 · There's a flaw in libxml2 in versions before 2.9.11.
    42Plan
  • ← EarlierCVE-2021-3517May 19, 2021 · There is a flaw in the xml entity encoding functionality of libxml2 in versions before 2.9.11.
    39Monitor
  • Later →CVE-2022-23308Feb 26, 2022 · valid.c in libxml2 before 2.9.13 has a use-after-free of ID and IDREF attributes.
    32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:libxml2-devel2.9.7-9.el8_4.2 · AlmaLinux:8Package registry (OSV)
alpine:libxml22.9.12-r0 · Alpine:v3.11Package registry (OSV)
debian:libxml22.9.10+dfsg-6.7 · Debian:12Package registry (OSV)
opensuse:libxml22.9.7-lp152.10.15.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:python-libxml2-python2.9.7-150000.3.57.1 · openSUSE:Leap 15.4Package registry (OSV)
red hat:jbcs-httpd24-apr-util0:1.6.1-91.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:jbcs-httpd24-apr-util-debuginfo0:1.6.1-91.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:jbcs-httpd24-apr-util-devel0:1.6.1-91.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:jbcs-httpd24-apr-util-ldap0:1.6.1-91.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:jbcs-httpd24-apr-util-mysql0:1.6.1-91.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:jbcs-httpd24-apr-util-nss0:1.6.1-91.jbcs.el7 · Red Hat:jboss_core_services:1::el7Package registry (OSV)
red hat:libxml20:2.9.7-9.el8_4.2 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:libxml2-debuginfo0:2.9.7-9.el8_4.2 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libxml2-debugsource0:2.9.7-9.el8_4.2 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libxml2-devel0:2.9.7-9.el8_4.2 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:python3-libxml20:2.9.7-9.el8_4.2 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:python3-libxml2-debuginfo0:2.9.7-9.el8_4.2 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
rocky linux:libxml20:2.9.7-9.el8_4.2 · Rocky Linux:8Package registry (OSV)
suse:libxml22.9.7-150000.3.57.1 · SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSSPackage registry (OSV)
suse:libxml22.9.7-3.37.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP2Package registry (OSV)
suse:python-libxml22.9.4-46.46.1 · SUSE:Linux Enterprise Server 12 SP5Package registry (OSV)
suse:python-libxml2-python2.9.7-150000.3.57.1 · SUSE:Linux Enterprise High Performance Computing 15 SP1-LTSSPackage registry (OSV)
suse:python-libxml2-python2.9.7-3.37.1 · SUSE:Linux Enterprise Module for Basesystem 15 SP2Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-776 · Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records