Oracle Java Runtime Environment - Heap Out-of-Bounds Read During OTF Font Rendering in glyph_CloseContour

A heap-based out-of-bounds read was observed in Oracle Java Runtime Environment version 8u202 (latest at the time of this writing) while fuzz-testing the processing of OpenType fonts. It manifests itself in the form of the following crash (with AFL's libdislocator):

--- cut ---
gdb$ c
  Continuing.
  Iteration (0,0)

  Thread 2 "java" received signal SIGSEGV, Segmentation fault.
  [----------------------------------registers-----------------------------------]
  RAX: 0x6d1a
  RBX: 0x7fffb5d94f48 --> 0x7fffb6319f00 --> 0x53ab1500ff
  RCX: 0xffffffffffff0000
  RDX: 0x7fff28fbdfe6 --> 0x2a001d00100003
  RSI: 0x7fff28fadfe8 --> 0x1e001100040000
  [...]
  [-------------------------------------code-------------------------------------]
     0x7fffb6395564 <glyph_CloseContour+148>:     mov    rsi,QWORD PTR [rbx+0x20]
     0x7fffb6395568 <glyph_CloseContour+152>:     add    rcx,rcx
     0x7fffb639556b <glyph_CloseContour+155>:     lea    rdi,[rdx+rcx*1-0x2]
  => 0x7fffb6395570 <glyph_CloseContour+160>:     movsx  rsi,WORD PTR [rsi+rcx*1-0x2]
     0x7fffb6395576 <glyph_CloseContour+166>:     mov    rdx,QWORD PTR [rbx+0x30]
     0x7fffb639557a <glyph_CloseContour+170>:     movsx  rcx,WORD PTR [rdi]
     0x7fffb639557e <glyph_CloseContour+174>:     movzx  r8d,WORD PTR [rdx+rcx*2]
     0x7fffb6395583 <glyph_CloseContour+179>:     cmp    WORD PTR [rdx+rsi*2],r8w
  [...]
  Stopped reason: SIGSEGV
  0x00007fffb6395570 in glyph_CloseContour () from jre/8u202/lib/amd64/libt2k.so

  gdb-peda$ where
  #0  0x00007fffb6395570 in glyph_CloseContour () from jre/8u202/lib/amd64/libt2k.so
  #1  0x00007fffb63ad71c in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #2  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #3  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #4  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #5  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #6  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #7  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #8  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #9  0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #10 0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #11 0x00007fffb63afa01 in Type2BuildChar () from jre/8u202/lib/amd64/libt2k.so
  #12 0x00007fffb63b469c in tsi_T2GetGlyphByIndex () from jre/8u202/lib/amd64/libt2k.so
  #13 0x00007fffb63b5655 in tsi_NewCFFClass () from jre/8u202/lib/amd64/libt2k.so
  #14 0x00007fffb63c73c8 in New_sfntClassLogical () from jre/8u202/lib/amd64/libt2k.so
  #15 0x00007fffb63a43e3 in Java_sun_font_T2KFontScaler_initNativeScaler () from jre/8u202/lib/amd64/libt2k.so
  #16 0x00007fffe5e376c7 in ?? ()
  #17 0x00007fff0003ccc0 in ?? ()
  #18 0x0000000000000000 in ?? ()
--- cut ---

The crash reproduces on both Windows and Linux platforms. On Windows, the crash can be observed with PageHeap enabled for the java.exe process:

--- cut ---
  (5f34.5d1c): Access violation - code c0000005 (first chance)
  First chance exceptions are reported before any exception handling.
  This exception may be expected and handled.
  t2k+0xfbec:
  00007ffa`0b4cfbec 4e0fbf4c50fe    movsx   r9,word ptr [rax+r10*2-2] ds:00000000`39c44ffe=????
  0:004> k
   # Child-SP          RetAddr           Call Site
  00 00000000`0d82de70 00007ffa`0b4e0c0d t2k+0xfbec
  01 00000000`0d82dea0 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x5305
  02 00000000`0d82df20 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  03 00000000`0d82dfa0 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  04 00000000`0d82e020 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  05 00000000`0d82e0a0 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  06 00000000`0d82e120 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  07 00000000`0d82e1a0 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  08 00000000`0d82e220 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  09 00000000`0d82e2a0 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  0a 00000000`0d82e320 00007ffa`0b4e2979 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  0b 00000000`0d82e3a0 00007ffa`0b4e3dd1 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x7071
  0c 00000000`0d82e420 00007ffa`0b4e4108 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x84c9
  0d 00000000`0d82e460 00007ffa`0b4e47e4 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x8800
  0e 00000000`0d82e4b0 00007ffa`0b4f07c5 t2k!Java_sun_font_T2KFontScaler_getGlyphCodeNative+0x8edc
  0f 00000000`0d82e500 00007ffa`0b4f0b11 t2k!Java_sun_font_T2KFontScaler_getGlyphVectorOutlineNative+0x72c9
  10 00000000`0d82e560 00007ffa`0b4d9ef6 t2k!Java_sun_font_T2KFontScaler_getGlyphVectorOutlineNative+0x7615
  11 00000000`0d82e5e0 00000000`0f928d27 t2k!Java_sun_font_T2KFontScaler_initNativeScaler+0x2c2
  12 00000000`0d82e650 00000000`2ad8f228 0xf928d27
  13 00000000`0d82e658 00000000`b0063339 0x2ad8f228
  14 00000000`0d82e660 00000000`0d82e730 0xb0063339
  15 00000000`0d82e668 00000000`b006f271 0xd82e730
  16 00000000`0d82e670 00000000`00000000 0xb006f271
  0:004> ? rax
  Evaluate expression: 969232384 = 00000000`39c55000
  0:004> ? r10
  Evaluate expression: -32768 = ffffffff`ffff8000
--- cut ---

Attached with this report are three mutated testcases, and a simple Java program used to reproduce the vulnerability by loading OpenType fonts specified through a command-line parameter.


Proof of Concept:
https://github.com/offensive-security/exploitdb-bin-sploits/raw/master/bin-sploits/46409.zip