# CVE-2016-7563: Artifex Software MuJS out-of-bounds read in chartorune

Source: https://junglewise.ai/threats/cve-2016-7563-artifex-software-mujs-out-of-bounds-read-in-chartorune  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-01-18. Updated: 2026-05-13  
License: CC BY 4.0 with a link back

CVE-2016-7563 · Severity: high · CVSS 7.5 · Published 2017-01-18

MuJS is a lightweight JavaScript interpreter used in various applications to execute scripts. A vulnerability was found where providing a specially crafted script ending with a specific character (an asterisk) can cause the software to crash. This could allow an attacker to disrupt services or applications that rely on MuJS to process untrusted input.

Technologies: [Artifex Mujs](https://junglewise.ai/threats/technologies/mujs). Vendors: [Artifex](https://junglewise.ai/threats/vendors/artifex).

## Quick answers

**Is CVE-2016-7563 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-7563 being exploited in the wild.

**How severe is CVE-2016-7563?** High severity, with a CVSS score of 7.5, published 18 January 2017.

**Which products and versions are affected?** Artifex Software MuJS unspecified.

**Is there a fix for CVE-2016-7563?** A patch was published on 2016-09-20: Fixed in commit f8234d830e17fc5e8fe09eb76d86dad3f6233c59 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2016-7563 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2016-7563?** Check whether you run Artifex Mujs. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out-of-bounds read (CWE-125) exists in the MuJS JavaScript engine within the `chartorune` function (located in `utf.c`). The root cause is in the lexical analyzer's `lexcomment` function, which fails to properly validate bounds when encountering a '*' character at the end of a multi-line comment. If the input ends abruptly with an asterisk, the engine unconditionally attempts to read the next character, leading to a 1-byte heap-buffer-overflow read. This can be triggered by providing a malicious JavaScript file or string to the interpreter, resulting in a crash (Denial of Service). The issue was addressed in commit f8234d830e17fc5e8fe09eb76d86dad3f6233c59.

## Affected products

- Artifex Software MuJS unspecified

## Timeline

- 2016-09-20: disclosed: Vulnerability reported by Shi Ji (@Puzzor)
- 2016-09-20: patched: Fixed in commit f8234d830e17fc5e8fe09eb76d86dad3f6233c59
- 2017-01-18: advisory: NVD publication date

## References

- [http://www.openwall.com/lists/oss-security/2016/09/21/5](http://www.openwall.com/lists/oss-security/2016/09/21/5)
- [http://www.openwall.com/lists/oss-security/2016/09/28/11](http://www.openwall.com/lists/oss-security/2016/09/28/11)
- [https://bugs.ghostscript.com/show_bug.cgi?id=697136](https://bugs.ghostscript.com/show_bug.cgi?id=697136)

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- [MuJS numeric conversion overflow in jsR_isindex](https://junglewise.ai/threats/cve-2026-88362-mujs-e892c9fdb-contains-an-incorrect-numeric-conversion)
- [Artifex Software MuJS integer overflow in MakeDay function](https://junglewise.ai/threats/cve-2017-5628-artifex-software-mujs-integer-overflow-in-makeday-function)
- [Artifex Software MuJS integer overflow in js_pushstring](https://junglewise.ai/threats/cve-2017-5627-artifex-software-mujs-integer-overflow-in-js-pushstring)
- [Artifex Software MuJS out-of-bounds read in chartorune](https://junglewise.ai/threats/cve-2016-9109-artifex-software-mujs-out-of-bounds-read-in-chartorune)
- [Artifex Software MuJS heap overflow in Fp_toString](https://junglewise.ai/threats/cve-2016-7564-artifex-software-mujs-heap-overflow-in-fp-tostring)