Null pointer dereference leading to crash of the server (splitVarVal)

[cve-reporting]

HTCPCP server incorrectly handles incoming network messages leading to a NULL pointer dereference, resulting in crash of the server.

Proposed CVSS 3.0 score:

7.5 (High) - CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Error message WITHOUT Address Sanitizer:

Welcome to the potLogic CoffeeTr0n!
    Ready to brew.. there are 5 Pots available
Created thread 0
Thread 0

Request:
D�����g�rd
Segmentation fault

---

Error message WITH Address Sanitizer:

./matrixssl-ASAN/apps/dtls/dtlsServer -p 44444
DTLS server running on port 44444
sslBuf = 0x61b00001e380 recvfromBuf = 0x61b00001f180 recvLen = 67
sslBuf = 0x61b00001ea80 recvfromBuf = 0x61b00001f180 recvLen = 1047
=================================================================
Created thread 0
Thread 0

Request:
D�����g�rd
ASAN:SIGSEGV
=================================================================
    ==21766==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7f2af2a2f746 bp 0x7f2aefbfbd10 sp 0x7f2aefbfb498 T1)
        #0 0x7f2af2a2f745 in strlen (/lib/x86_64-linux-gnu/libc.so.6+0x8b745)
        #1 0x7f2af2ffb1a5 in __interceptor_strlen (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x701a5)
        #2 0x40347b in splitVarVal (htcpcp_server_ASAN+0x40347b)
        #3 0x40392b in CoffeeRequestHandler (htcpcp_server_ASAN+0x40392b)
        #4 0x403e47 in thread (htcpcp_server_ASAN+0x403e47)
        #5 0x7f2af2d756b9 in start_thread (/lib/x86_64-linux-gnu/libpthread.so.0+0x76b9)
        #6 0x7f2af2aab41c in clone (/lib/x86_64-linux-gnu/libc.so.6+0x10741c)

    AddressSanitizer can not provide additional info.
    SUMMARY: AddressSanitizer: SEGV ??:0 strlen
    Thread T1 created by T0 here:
        #0 0x7f2af2fc1253 in pthread_create (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x36253)
        #1 0x404b09 in main (htcpcp_server_ASAN+0x404b09)
        #2 0x7f2af29c482f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

    ==21766==ABORTING

---

Reproduction:

1. Download and compile HTCPCP server.

2. Run HTCPCP server: ./htcpcp_server 44444

(using defork from Preeny package: https://github.com/zardus/preeny) LD_PRELOAD=~/tools/preeny/defork.so ./htcpcp_server 44444

3. Unzip and send attached crafted message e.g. using netcat: netcat $IP 44444 < payload_madmaze-htcpcp_000.raw where $IP is IP of test server

payload_madmaze-htcpcp_000.raw.zip