Cesanta mJS up to 1.26 src/mjs_tok.c skip_spaces_and_comments heap-based overflow

Summaryinfo

A vulnerability has been found in Cesanta mJS up to 1.26 and classified as critical. Affected by this vulnerability is the function skip_spaces_and_comments of the file src/mjs_tok.c. The manipulation leads to heap-based overflow. This vulnerability is listed as CVE-2026-86716. The attack may be initiated remotely. In addition, an exploit is available. The project was informed of the problem early through an issue report but has not responded yet.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Cesanta mJS up to 1.26. This issue affects the function skip_spaces_and_comments of the file src/mjs_tok.c. The manipulation with an unknown input leads to a heap-based overflow vulnerability. Using CWE to declare the problem leads to CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). Impacted is confidentiality, integrity, and availability.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-86716. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details as well as a public exploit are known.

The exploit is available at github.com. It is declared as proof-of-concept. The project was informed of the problem early through an issue report but has not responded yet.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• Cesanta

Name

• mJS

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26

License

• commercial

Website

• Product: https://github.com/cesanta/mjs/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
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CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Submitinfo

Accepted

• Submit #910881: cesanta mJS v1.26 Heap-based Buffer Overflow (by lrrh)

Duplicate

• Submit #XXXXXX: Xxxxxxx Xxx Xx.xx Xxxx-xxxxx Xxxxxx Xxxxxxxx (by lrrh)

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