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CVE-2021-39207

28
FAUCET Score

CVE-2021-39207 is a critical YAML deserialization vulnerability affecting Facebook's ParlAI framework, which allows for arbitrary code execution due to unsafe loading practices. With a CVSS score of 8.8 (High), this vulnerability can be exploited remotely with low complexity and user interaction, leading to high impact on confidentiality, integrity, and availability. While there is no evidence of active exploitation, public exploit code, or significant community discussion, users are strongly advised to upgrade to ParlAI version 1.1.0 or later, or implement the recommended workaround of using SafeLoader.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.1.0CPE matchmatch criteria
cpe:2.3:a:facebook:parlai:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.4HIGH

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
LOW
Exploitability Score
1.8
Impact Score
6.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.79%
Probability of exploitation in next 30 days
EPSS Percentile
76.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0179 is in the 74th percentile among its peer group of 17,844 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: parlaiFixed in: 1.1.0

Vendor Advisories (1)

pipGHSA-m87f-9fvv-2mggmedium

Deserialization of Untrusted Data in parlai

Sep 13, 2021

References

github.com / facebookresearch/ParlAI/commit/4374fa2aba383db6526ab36e939eb1cf8ef99879
PatchThird Party Advisory
github.com / facebookresearch/ParlAI/commit/507d066ef432ea27d3e201da08009872a2f37725
PatchThird Party Advisory
github.com / facebookresearch/ParlAI/security/advisories/GHSA-m87f-9fvv-2mgg
PatchThird Party Advisory