How severe is CVE-2021-24040?

CVE-2021-24040 has a CVSS 3.x base score of 9.8, 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 high, and availability high.

Is CVE-2021-24040 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 17% (97th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-24040?

CVE-2021-24040 affects Facebook Parlai. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-24040?

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-2021-24040 published?

CVE-2021-24040 was published on 2021-09-10 and last updated on 2026-06-17.

CVE-2021-24040

CVE-2021-24040 is a critical-severity vulnerability in Facebook Parlai with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 17% places it in the 97th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-502.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 17% (97th 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

Due to use of unsafe YAML deserialization logic, an attacker with the ability to modify local YAML configuration files could provide malicious input, resulting in remote code execution or similar risks. This issue affects ParlAI prior to v1.1.0.

Frequently asked questions

What is CVE-2021-24040?: Due to use of unsafe YAML deserialization logic, an attacker with the ability to modify local YAML configuration files could provide malicious input, resulting in remote code execution or similar risks. This issue affects ParlAI prior to v1.1.0.
How severe is CVE-2021-24040?: CVE-2021-24040 has a CVSS 3.x base score of 9.8, 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 high, and availability high.
Is CVE-2021-24040 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 17% (97th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-24040?: CVE-2021-24040 affects Facebook Parlai. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-24040?: 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-2021-24040 published?: CVE-2021-24040 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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