CPU can crack the password but GPU can't
#1
Hi.
I have problem on Hybrid attack mode (-a 6). When i try to crack an md5crypt hash with -a 6, Hashcat can't crack the password using only GPU. But if i force to use only CPU (-D 1) with the same attack mode, it cracks the password without any problem.

The command i use:
hashcat hash.txt -m 500 -a 6 word.txt ?d?d

hash.txt content:
root:$1$XX$.XXXXXXXXXXXXXXXXg1KQ0:0:0:root:/root/:/bin/psh

word.txt content:
testpsw
XXXXXXXXXXpav


The correct password is XXXXXXXXXXpav33, but hashcat can't crack it using only GPU. I also tried replacing the lines. It tries the correct password, but can't crack it:


Code:
Candidate.Engine.: Device Generator
Candidates.#1....: testpsw33 -> XXXXXXXXXXpav33


If i force to use only CPU, it cracks without any problem:


Code:
hashcat hash.txt -m 500 -a 6 word.txt ?d?d -D 1

$1$XX$.XXXXXXXXXXXXXXXXg1KQ0:XXXXXXXXXXpav33


Another interesting thing is, when i add any character to the testpsw (for example testtpsw), it cracks the password on GPU too. So when there is another line in the word.txt file which is 7 characters long, it fails to crack. When its length lower than 7 or higher than 7, it cracks the password on GPU too.

Hashcat version info
Code:
hashcat -I
hashcat (v6.2.6) starting in backend information mode

OpenCL Info:
============

OpenCL Platform ID #1
  Vendor..: Intel(R) Corporation
  Name....: Intel(R) OpenCL HD Graphics
  Version.: OpenCL 3.0

  Backend Device ID #1
    Type...........: GPU
    Vendor.ID......: 8
    Vendor.........: Intel(R) Corporation
    Name...........: Intel(R) UHD Graphics
    Version........: OpenCL 3.0 NEO
    Processor(s)...: 80
    Clock..........: 1300
    Memory.Total...: 3146 MB (limited to 786 MB allocatable in one block)
    Memory.Free....: 1536 MB
    Local.Memory...: 64 KB
    OpenCL.Version.: OpenCL C 1.2
    Driver.Version.: 31.0.101.3959

OpenCL Platform ID #2
  Vendor..: Intel(R) Corporation
  Name....: Intel(R) OpenCL
  Version.: OpenCL 3.0 WINDOWS

  Backend Device ID #2
    Type...........: CPU
    Vendor.ID......: 8
    Vendor.........: Intel(R) Corporation
    Name...........: 12th Gen Intel(R) Core(TM) i5-1240P
    Version........: OpenCL 3.0 (Build 0)
    Processor(s)...: 16
    Clock..........: 0
    Memory.Total...: 7865 MB (limited to 1966 MB allocatable in one block)
    Memory.Free....: 3900 MB
    Local.Memory...: 256 KB
    OpenCL.Version.: OpenCL C 3.0
    Driver.Version.: 2025.19.3.0.17_230222

I tried the same attack mode with the same files (which fails to crack on Hashcat) on John the Ripper using only GPU (format=md5crypt-opencl), it cracks without any problem.
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