CVE-2021-31875
CVSS v3
9.8
CRITICAL
EPSS Score
2.2 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
In mjs_json.c in Cesanta MongooseOS mJS 1.26, a maliciously formed JSON string can trigger an off-by-one heap-based buffer overflow in mjs_json_parse, which can potentially lead to redirection of control flow. NOTE: the original reporter disputes the significance of this finding because "there isn’t very much of an opportunity to exploit this reliably for an information leak, so there isn’t any real security impact."
Technical details
- Published
- 2021-04-29
Frequently asked questions
What is CVE-2021-31875?
In mjs_json.c in Cesanta MongooseOS mJS 1.26, a maliciously formed JSON string can trigger an off-by-one heap-based buffer overflow in mjs_json_parse, which can potentially lead to redirection of control flow. NOTE: the original reporter disputes the significance of this finding because "there isn’t very much of an opportunity to exploit this reliably for an information leak, so there isn’t any real security impact."
Is CVE-2021-31875 actively exploited?
Active exploitation of CVE-2021-31875 has not been confirmed. Its EPSS score was 2.2% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2021-31875?
CVE-2021-31875 has a CVSS v3 base score of 9.8 (CRITICAL severity).
Is CVE-2021-31875 affecting your environment?
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