Find pattern on multiple lines within BIG log files

Here's a way you can do it in python (I added to your example a bit to prove that you can still get the matches you desire even if there are random single lines of AAAAAAAAA, BBBBBBBBB, or CCCCCCCCC dispersed throughout the logfile) :

below are the contents of find_log_vulns.py

#! /usr/bin/python3

import re

test_string = """1234324
AAAAAAAAA
BBBBBBBBB
CCCCCCCCC
absdfjv4er4
AAAAAAAAA
BBBBBBBBB
CCCCCCCCC
123466666
AAAAAAAAA
ghrhvhhhfh
BBBBBBBBB
fjwjefjsjfjwjf
CCCCCCCCC
24wfsgggg
AAAAAAAAA
BBBBBBBBB
CCCCCCCCC
zzzz"""

matches = re.findall('AAAAAAAAA\nBBBBBBBBB\nCCCCCCCCC\n', test_string, re.MULTILINE)

print(matches)

The result I get from running the above:

$ ./find_log_vulns.py
['AAAAAAAAA\nBBBBBBBBB\nCCCCCCCCC\n', 'AAAAAAAAA\nBBBBBBBBB\nCCCCCCCCC\n', 'AAAAAAAAA\nBBBBBBBBB\nCCCCCCCCC\n']

As shown above, each match will be returned as an element in a list.

using ripgrep:

rg -U 'A+\nB+\nC+' in
2:AAAAAAAAA
3:BBBBBBBBB
4:CCCCCCCCC
6:AAAAAAAAA
7:BBBBBBBBB
8:CCCCCCCCC
16:AAAAAAAAA
17:BBBBBBBBB
18:CCCCCCCCC

you can get rid of the line numbers, and so on. If you need separators between the matches you can do this:

rg -U 'A+\nB+\nC+' in | rg --passthru -e '(^A)' -r $'\n'A

AAAAAAAAA
BBBBBBBBB
CCCCCCCCC

AAAAAAAAA
BBBBBBBBB
CCCCCCCCC

AAAAAAAAA
BBBBBBBBB
CCCCCCCCC

Using awk:

awk -v ptrn="AAAAAAAAA\0BBBBBBBBB\0CCCCCCCCC\0" '
BEGIN{ split(ptrn, tmp, "\0"); lngth=gsub("\0", "", ptrn ) }
$0 ~ tmp[++fieldNr]{ buf=(buf==""?"": buf OFS) NR":"$0 ;
                     if ( fieldNr == lngth ) { print buf; exit }
                     next
                   }
{ fieldNr=0; buf="" }' infile

this will give you the line number followed by the matched line content; here we used "Partial Regexp Match" using the patterns from the "ptrn" against the lines. see How do I find the text that matches a pattern? for other matching options.

we used NUL character \0 to separate patterns.

Sample input:

AAAAAAAAA
BBBBBBBBB

CCCCCCCCC
AAAAAAAAA
BBBBBBBBB
ccccccccc
123AAAAAAAAA
BBBBBBBBB123
123CCCCCCCCC3

Output:

8:123AAAAAAAAA 9:BBBBBBBBB123 10:123CCCCCCCCC3

Just for fun with good old awk

cat file | wc -l
21287021

with > 3000,000 matches

time awk 'BEGIN{getline; a=$0; getline; b=$0}
       $0~/^C+$/ && a~/^A+$/ && b~/^B+$/{print "match starting on line "NR-2 }{a=b;b=$0}' file

real    0m12.644s
user    0m7.149s
sys     0m4.314s

Compared with rgon my machine

time rg -U 'A+\nB+\nC+' file
real    0m40.322s
user    0m16.503s
sys     0m17.246s