How severe is CVE-2021-3828?

CVE-2021-3828 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-3828 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-3828?

CVE-2021-3828 affects Nltk. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-3828?

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

When was CVE-2021-3828 published?

CVE-2021-3828 was published on 2021-09-27 and last updated on 2026-06-17.

CVE-2021-3828

CVE-2021-3828 is a high-severity vulnerability in Nltk with a CVSS 3.x base score of 7.5. 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-697.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 2% (74th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-697
Affected product: Nltk
Published: 2021-09-27
Last modified: 2026-06-17

Description

nltk is vulnerable to Inefficient Regular Expression Complexity

Frequently asked questions

What is CVE-2021-3828?: nltk is vulnerable to Inefficient Regular Expression Complexity
How severe is CVE-2021-3828?: CVE-2021-3828 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-3828 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-3828?: CVE-2021-3828 affects Nltk. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-3828?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-3828 published?: CVE-2021-3828 was published on 2021-09-27 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nltk:nltk:*:*:*:*:*:*:*:*

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