How severe is CVE-2019-12951?

CVE-2019-12951 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-2019-12951 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-12951?

CVE-2019-12951 affects Cesanta Mongoose. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2019-12951?

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-2019-12951 published?

CVE-2019-12951 was published on 2019-06-24 and last updated on 2026-06-17.

CVE-2019-12951

CVE-2019-12951 is a critical-severity vulnerability in Cesanta Mongoose with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Cesanta Mongoose
Published: 2019-06-24
Last modified: 2026-06-17

Description

An issue was discovered in Mongoose before 6.15. The parse_mqtt() function in mg_mqtt.c has a critical heap-based buffer overflow.

Frequently asked questions

What is CVE-2019-12951?: An issue was discovered in Mongoose before 6.15. The parse_mqtt() function in mg_mqtt.c has a critical heap-based buffer overflow.
How severe is CVE-2019-12951?: CVE-2019-12951 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-2019-12951 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-12951?: CVE-2019-12951 affects Cesanta Mongoose. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2019-12951?: 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-2019-12951 published?: CVE-2019-12951 was published on 2019-06-24 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*

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CVE-2019-19307 — Critical (CVSS 9.8): An integer overflow in parse_mqtt in mongoose.c in Cesanta Mongoose 6.16 allows an attacker to achieve remote DoS…
CVE-2018-20356 — Critical (CVSS 9.8): An invalid read of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in…
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CVE-2018-20354 — Critical (CVSS 9.8): An invalid read of 8 bytes due to a use-after-free vulnerability during a "return" in the mg_http_get_proto_data…

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