How severe is CVE-2021-44557?

CVE-2021-44557 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability high.

Is CVE-2021-44557 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-44557?

CVE-2021-44557 affects Kb Multiner. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-44557?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-44557 published?

CVE-2021-44557 was published on 2021-12-08 and last updated on 2026-06-17.

CVE-2021-44557

CVE-2021-44557 is a critical-severity vulnerability in Kb Multiner with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-611.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v2: 6.4
EPSS exploit prediction: 1% (66th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-611
Affected product: Kb Multiner
Published: 2021-12-08
Last modified: 2026-06-17

Description

National Library of the Netherlands multiNER <= c0440948057afc6e3d6b4903a7c05e666b94a3bc is affected by an XML External Entity (XXE) vulnerability in multiNER/ner.py. Since XML parsing resolves external entities, a malicious XML stream could leak internal files and/or cause a DoS.

Frequently asked questions

What is CVE-2021-44557?: National Library of the Netherlands multiNER <= c0440948057afc6e3d6b4903a7c05e666b94a3bc is affected by an XML External Entity (XXE) vulnerability in multiNER/ner.py. Since XML parsing resolves external entities, a malicious XML stream could leak internal files and/or cause a DoS.
How severe is CVE-2021-44557?: CVE-2021-44557 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability high.
Is CVE-2021-44557 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-44557?: CVE-2021-44557 affects Kb Multiner. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-44557?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-44557 published?: CVE-2021-44557 was published on 2021-12-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:kb:multiner:*:*:*:*:*:*:*:*

Other CWE-611 (Improper Restriction of XML External Entity Reference (XXE)) vulnerabilities

CVE-2022-22486 — Critical (CVSS 10.0): IBM Tivoli Workload Scheduler 9.4, 9.5, and 10.1 is vulnerable to an XML External Entity Injection (XXE) attack when…
CVE-2019-14678 — Critical (CVSS 10.0): SAS XML Mapper 9.45 has an XML External Entity (XXE) vulnerability that can be leveraged by malicious attackers in…
CVE-2015-9280 — Critical (CVSS 10.0): MailEnable before 8.60 allows XXE via an XML document in the request.aspx Options parameter.
CVE-2018-1000838 — Critical (CVSS 10.0): autopsy version <= 4.9.0 contains a XML External Entity (XXE) vulnerability in CaseMetadata XML Parser that can result…
CVE-2018-1000837 — Critical (CVSS 10.0): UML Designer version <= 8.0.0 contains a XML External Entity (XXE) vulnerability in XML parser for plugins that can…
CVE-2018-1000835 — Critical (CVSS 10.0): KeePassDX version <= 2.5.0.0beta17 contains a XML External Entity (XXE) vulnerability in kdbx file parser that can…

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