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Fencer Vulns
critical 9.8

CVE-2021-24040 in the critical feed json

Deserialization of Untrusted Data in parlai

published 2021-09-10 5 y ago modified 2026-07-09 4 mo ago also CVE-2021-39207 , GHSA-m87f-9fvv-2mgg , GHSA-mwgj-7x7j-6966 , PYSEC-2021-330 , PYSEC-2021-334 , EUVD-2021-0165

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
17.4%
EPSS 17.4% chance of exploitation in 30 days, percentile 97%
public exploits
1
Exploit-DB

Summary

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.

Patch / fix

  • pypi parlai 1.1.0
  • Facebook ParlAI 1.1.0

Timeline

  1. Published
  2. First public exploit (EDB-50289)

Exploit prediction

17.35% chance of exploitation in the next 30 days, higher than 97% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • EDB-50289 Facebook ParlAI 1.0.0 - Deserialization of Untrusted Data in parlai local, 2021-09-13
  • packetstormsecurity.com http://packetstormsecurity.com/files/164136/Facebook-ParlAI-1.0.0-Code-Execution-Deserialization.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
GitHub 3.1 8.4 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:L

Affected packages

ecosystem package affected fixed in
pypi parlai
<1.1.0
1.1.0

Affected products

  • Facebook ParlAI

Classification

Weakness
  • CWE-502 Deserialization of Untrusted Data

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.