How severe is CVE-2021-39207?

CVE-2021-39207 has a CVSS 3.x base score of 8.4, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.

Is CVE-2021-39207 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39207?

CVE-2021-39207 affects Facebook Parlai. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-39207?

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-2021-39207 published?

CVE-2021-39207 was published on 2021-09-10 and last updated on 2026-06-17.

CVE-2021-39207

CVE-2021-39207 is a high-severity vulnerability in Facebook Parlai with a CVSS 3.x base score of 8.4. 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-502.

Key facts

Severity: High (CVSS 3.x base score 8.4)
CVSS v2: 6.5
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Facebook Parlai
Published: 2021-09-10
Last modified: 2026-06-17

Description

parlai is a framework for training and evaluating AI models on a variety of openly available dialogue datasets. In affected versions the package is vulnerable to YAML deserialization attack caused by unsafe loading which leads to Arbitary code execution. This security bug is patched by avoiding unsafe loader users should update to version above v1.1.0. If upgrading is not possible then users can change the Loader used to SafeLoader as a workaround. See commit 507d066ef432ea27d3e201da08009872a2f37725 for details.

Frequently asked questions

What is CVE-2021-39207?: parlai is a framework for training and evaluating AI models on a variety of openly available dialogue datasets. In affected versions the package is vulnerable to YAML deserialization attack caused by unsafe loading which leads to Arbitary code execution. This security bug is patched by avoiding unsafe loader users should update to version above v1.1.0. If upgrading is not possible then users can change the Loader used to SafeLoader as a workaround. See commit 507d066ef432ea27d3e201da08009872a2f37725 for details.
How severe is CVE-2021-39207?: CVE-2021-39207 has a CVSS 3.x base score of 8.4, rated high severity. It is exploitable over network with high attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability low.
Is CVE-2021-39207 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39207?: CVE-2021-39207 affects Facebook Parlai. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-39207?: 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-2021-39207 published?: CVE-2021-39207 was published on 2021-09-10 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:facebook:parlai:*:*:*:*:*:*:*:*

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