How severe is CVE-2021-39521?

CVE-2021-39521 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-39521 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39521?

CVE-2021-39521 affects Gnu Libredwg. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-39521?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-39521 published?

CVE-2021-39521 was published on 2021-09-20 and last updated on 2026-06-17.

CVE-2021-39521

CVE-2021-39521 is a medium-severity vulnerability in Gnu Libredwg with a CVSS 3.x base score of 6.5. 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-476.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.3
EPSS exploit prediction: 1% (53rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-476
Affected product: Gnu Libredwg
Published: 2021-09-20
Last modified: 2026-06-17

Description

An issue was discovered in libredwg through v0.10.1.3751. A NULL pointer dereference exists in the function bit_read_BB() located in bits.c. It allows an attacker to cause Denial of Service.

Frequently asked questions

What is CVE-2021-39521?: An issue was discovered in libredwg through v0.10.1.3751. A NULL pointer dereference exists in the function bit_read_BB() located in bits.c. It allows an attacker to cause Denial of Service.
How severe is CVE-2021-39521?: CVE-2021-39521 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-39521 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39521?: CVE-2021-39521 affects Gnu Libredwg. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-39521?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-39521 published?: CVE-2021-39521 was published on 2021-09-20 and last updated on 2026-06-17.

References

https://github.com/LibreDWG/libredwg/issues/262

Affected products (1)

cpe:2.3:a:gnu:libredwg:*:*:*:*:*:*:*:*

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