CVE-2021-3541 — A flaw was found in libxml2. Exponential entity expansion attack its possible bypassing all...

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

• Documented patch — bugzilla.redhat.com (NIST National Vulnerability Database)
• Documented patch — www.oracle.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (Netapp Active Iq Unified Manager, Netapp Cloud Backup, Netapp Clustered Data Ontap…).
2. Apply the fixed version or the patch documented under Remediation.
3. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-776

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 2.07%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

Timeline

What happened to this CVE, newest first.

• 2026
• Record published
  Oct 14, 2026
• Fix documented
  Oct 14, 2026 · NIST National Vulnerability Database
• Affected products added · xmlsoft/libxml2, redhat/jboss core services, oracle/zfs storage appliance kit, netapp/active iq unified manager, netapp/
  Oct 14, 2026 · NIST National Vulnerability Database
• CVSS changed · 6.5
  Oct 14, 2026 · NIST National Vulnerability Database
• Source status changed · → Modified
  Oct 14, 2026 · NIST National Vulnerability Database
• Record created in this database
  Oct 14, 2026 · Alertas do Telegram
• 2021
• CVE published
  Jul 9, 2021 · redhat

Source activity

Repeated readings are counted rather than listed.

• 2× References added · Oct 14, 2026 – Oct 14, 2026
• 1× Official description updated · Oct 14, 2026 – Oct 14, 2026

References

6 on the record

• bugzilla.redhat.com/show_bug.cgi
  Issue Tracking, Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• www.oracle.com/security-alerts/cpujan2022.html
  Patch, Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
• github.com/advisories/GHSA-wcgr-63g6-pj93
  GitHub Security Advisories
• nvd.nist.gov/vuln/detail/CVE-2021-3541
  GitHub Security Advisories
• cert-portal.siemens.com/productcert/html/ssa-398330.html
  NIST National Vulnerability Database
• security.netapp.com/advisory/ntap-20210805-0007/
  Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

Related CVEs (same products)

• High CVE-2026-86143 In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and… Sep 5, 2026
• Low CVE-2026-86141 Unchecked Return Value in Xmlsoft Libxml2 Sep 5, 2026
• High CVE-2026-86142 Heap-based Buffer Overflow in Xmlsoft Libxml2 Sep 5, 2026
• High CVE-2026-86144 Incorrect Resource Transfer Between Spheres in Xmlsoft Libxml2 Sep 5, 2026
• High CVE-2026-86140 Stack-based Buffer Overflow in Xmlsoft Libxml2 Sep 5, 2026
• High CVE-2026-86139 Integer Overflow or Wraparound in Xmlsoft Libxml2 Sep 5, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No CISA SSVC assessment.
• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-3541 is "A flaw was found in libxml2. Exponential entity expansion attack its possible bypassing all...", rated Medium. It affects Active Iq Unified Manager (Netapp); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. EPSS 2.07% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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