CVE-2026-5244
CVE-2026-5244 is a high-severity vulnerability in Cesanta Mongoose with a CVSS 3.x base score of 7.3. 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-119.
Key facts
- Severity: High (CVSS 3.x base score 7.3)
- CVSS v2: 7.5
- CVSS v4: 5.5
- EPSS exploit prediction: 1% (50th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-18170
- Weakness: CWE-119
- Affected product: Cesanta Mongoose
- Published:
- Last modified:
Description
A vulnerability has been found in Cesanta Mongoose up to 7.20. This affects the function mg_tls_recv_cert of the file mongoose.c of the component TLS 1.3 Handler. Such manipulation of the argument pubkey leads to heap-based buffer overflow. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 7.21 mitigates this issue. The name of the patch is 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. It is advisable to upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.
Frequently asked questions
- What is CVE-2026-5244?
- A vulnerability has been found in Cesanta Mongoose up to 7.20. This affects the function mg_tls_recv_cert of the file mongoose.c of the component TLS 1.3 Handler. Such manipulation of the argument pubkey leads to heap-based buffer overflow. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 7.21 mitigates this issue. The name of the patch is 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. It is advisable to upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.
- How severe is CVE-2026-5244?
- CVE-2026-5244 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
- Is CVE-2026-5244 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-5244?
- CVE-2026-5244 affects Cesanta Mongoose. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-5244?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-5244 have an EU (EUVD) identifier?
- Yes. CVE-2026-5244 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18170.
- When was CVE-2026-5244 published?
- CVE-2026-5244 was published on 2026-04-02 and last updated on 2026-06-17.
References
- https://github.com/cesanta/mongoose/
- https://github.com/cesanta/mongoose/commit/0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1
- https://github.com/cesanta/mongoose/releases/tag/7.21
- https://vuldb.com/submit/770063
- https://vuldb.com/vuln/354825
- https://vuldb.com/vuln/354825/cti
Affected products (1)
- cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*
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- CVE-2020-25756 — Critical (CVSS 9.8): A buffer overflow vulnerability exists in the mg_get_http_header function in Cesanta Mongoose 6.18 due to a lack of…
- 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-2019-12951 — Critical (CVSS 9.8): An issue was discovered in Mongoose before 6.15. The parse_mqtt() function in mg_mqtt.c has a critical heap-based…
- 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…
- CVE-2018-20355 — Critical (CVSS 9.8): An invalid write of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in…
All CVEs affecting Cesanta Mongoose →
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