How severe is CVE-2020-25756?

CVE-2020-25756 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-2020-25756 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-25756?

CVE-2020-25756 affects Cesanta Mongoose. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-25756?

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-2020-25756 published?

CVE-2020-25756 was published on 2020-09-18 and last updated on 2026-06-17.

CVE-2020-25756

CVE-2020-25756 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-120.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (73rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-120
Affected product: Cesanta Mongoose
Published: 2020-09-18
Last modified: 2026-06-17

Description

A buffer overflow vulnerability exists in the mg_get_http_header function in Cesanta Mongoose 6.18 due to a lack of bounds checking. A crafted HTTP header can exploit this bug. NOTE: a committer has stated "this will not happen in practice.

Frequently asked questions

What is CVE-2020-25756?: A buffer overflow vulnerability exists in the mg_get_http_header function in Cesanta Mongoose 6.18 due to a lack of bounds checking. A crafted HTTP header can exploit this bug. NOTE: a committer has stated "this will not happen in practice.
How severe is CVE-2020-25756?: CVE-2020-25756 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-2020-25756 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (73rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-25756?: CVE-2020-25756 affects Cesanta Mongoose. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-25756?: 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-2020-25756 published?: CVE-2020-25756 was published on 2020-09-18 and last updated on 2026-06-17.

References

https://github.com/cesanta/mongoose/issues/1135

Affected products (1)

cpe:2.3:a:cesanta:mongoose:6.18:*:*:*:*:*:*:*

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