CVE-2026-6986

Description

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

CVSS v3.1 Score

3.7

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.00%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-345 CWE-345

CWE-347 CWE-347

Affected Products

Vendor	Product	Versions
cesanta	mongoose	7.0 — 7.21

References

Exploits

https://github.com/dwBruijn/CVEs/blob/main/Mongoose/AESGCM.md

Other References

https://github.com/cesanta/mongoose/releases/tag/7.21 https://vuldb.com/submit/796231 https://vuldb.com/vuln/359529 https://vuldb.com/vuln/359529/cti

Frequently Asked Questions

What is CVE-2026-6986? +

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already. It has a CVSS v3.1 base score of 3.7 (LOW).

How severe is CVE-2026-6986? +

CVE-2026-6986 has a CVSS v3.1 score of 3.7 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-6986? +

CVE-2026-6986 affects products from cesanta, specifically: mongoose. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-6986? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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