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Fencer Vulns
low 3.7

CVE-2021-21970 json

An out-of-bounds write vulnerability exists in the HandleSeaCloudMessage functionality of Sealevel Systems, Inc.

published 2022-02-04 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-9141

cvss
3.7
version 3.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits
0
none known

Summary

An out-of-bounds write vulnerability exists in the HandleSeaCloudMessage functionality of Sealevel Systems, Inc. SeaConnect 370W v1.3.34. The HandleIncomingSeaCloudMessage function uses at [3] the json_object_get_string to populate the p_name global variable. The p_name is only 0x80 bytes long, and the total MQTT message could be up to 0x201 bytes. Because the function json_object_get_string will fill str based on the length of the json’s value and not the actual str size, this would result in a possible out-of-bounds write.

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
18 mo ago

Exploit prediction

0.89% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • talosintelligence.com https://talosintelligence.com/vulnerability_reports/TALOS-2021-1396 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.0 3.7 CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • n/a Sealevel

Classification

Weakness
  • CWE-120 Buffer Copy without Checking Size of Input
  • CWE-787 Out-of-bounds Write

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.