Your message dated Tue, 18 Aug 2026 21:48:31 +0000
with message-id <[email protected]>
and subject line Bug#1142905: fixed in unzip 6.0-29+deb13u1
has caused the Debian Bug report #1142905,
regarding unzip: stack out-of-bounds NUL write in EF_SMARTZIP handler
[CAN-2026-2034443]
to be marked as done.
This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.
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--
1142905: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1142905
Debian Bug Tracking System
Contact [email protected] with problems
--- Begin Message ---
Package: unzip
Version: 6.0-28
Severity: grave
Tags: security
X-Debbugs-Cc: [email protected], [email protected]
Hi,
InfoZIP unzip 6.0 contains a stack out-of-bounds NUL byte write in the
EF_SMARTZIP (ID 0x4d63) extra field handler in zipinfo.c. An attacker-
controlled byte from the extra field data is used as an array index to
NUL-terminate a 32-byte stack buffer, without any bounds check.
CAN: CAN-2026-2034443 (pending assignment from MITRE)
CWE: CWE-787 (Out-of-bounds Write) / CWE-121 (Stack-based Buffer Overflow)
CVSS: High (stack OOB write)
ROOT CAUSE (zipinfo.c, lines 1766-1769):
case EF_SMARTZIP:
if ((eb_datalen == EB_SMARTZIP_HLEN) &&
makelong(ef_ptr) == 0x70695A64 /* "dZip" */) {
char filenameBuf[32]; // 32-byte stack buffer
zi_showMacTypeCreator(__G__ &ef_ptr[4]);
memcpy(filenameBuf, &ef_ptr[33], 31); // copies 31 bytes (safe)
filenameBuf[ef_ptr[32]] = '\0'; // NUL WRITE at attacker-
// controlled index!
...
ef_ptr[32] is a byte from the extra field data (attacker-controlled,
range 0-255). filenameBuf is only 32 bytes (indices 0-31 valid). When
ef_ptr[32] > 31, the NUL write lands past the stack buffer boundary.
With ef_ptr[32] = 200, the write is at offset 200 — 168 bytes past
the end of the 32-byte buffer.
TRIGGER: zipinfo poc.zip (or unzip -Z -v poc.zip) where poc.zip has
a file with an EF_SMARTZIP extra field (ID 0x4d63) of exactly
EB_SMARTZIP_HLEN bytes, magic "dZip" at offset 0, and byte value > 31
at offset 32.
ASAN OUTPUT:
==8==ERROR: AddressSanitizer: stack-buffer-overflow on address
0xffffeb74aeb8 at pc 0xaaaad8522268
WRITE of size 1 at 0xffffeb74aeb8 thread T0
#0 0xaaaad8522264 (zipinfo.c, EF_SMARTZIP handler)
Address 0xffffeb74aeb8 is located in stack of thread T0:
[336, 368) 'filenameBuf.i' (line 1704)
Memory access at offset 536 overflows this variable (32 bytes at
stack offset 336-368, write landed at offset 536 = 168 bytes past
the end).
IMPACT: Stack buffer overflow (single NUL byte) with attacker-
controlled offset. While limited to writing a NUL byte, the offset
into the stack is fully controlled (0-255), allowing corruption of
saved frame pointers, local variables, or return addresses depending
on stack layout. At minimum: crash (DoS). Triggered by a user running
zipinfo on a crafted ZIP file.
SUGGESTED FIX:
memcpy(filenameBuf, &ef_ptr[33], 31);
- filenameBuf[ef_ptr[32]] = '\0';
+ {
+ unsigned idx = (unsigned)ef_ptr[32];
+ if (idx > 31) idx = 31;
+ filenameBuf[idx] = '\0';
+ }
Or more conservatively, always NUL-terminate at index 31:
memcpy(filenameBuf, &ef_ptr[33], 31);
filenameBuf[31] = '\0';
Best regards,
Akhil Koul
--- End Message ---
--- Begin Message ---
Source: unzip
Source-Version: 6.0-29+deb13u1
Done: Santiago Vila <[email protected]>
We believe that the bug you reported is fixed in the latest version of
unzip, which is due to be installed in the Debian FTP archive.
A summary of the changes between this version and the previous one is
attached.
Thank you for reporting the bug, which will now be closed. If you
have further comments please address them to [email protected],
and the maintainer will reopen the bug report if appropriate.
Debian distribution maintenance software
pp.
Santiago Vila <[email protected]> (supplier of updated unzip package)
(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing [email protected])
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
Format: 1.8
Date: Tue, 11 Aug 2026 00:10:00 +0200
Source: unzip
Architecture: source
Version: 6.0-29+deb13u1
Distribution: trixie-security
Urgency: high
Maintainer: Santiago Vila <[email protected]>
Changed-By: Santiago Vila <[email protected]>
Closes: 1142904 1142905 1142906
Changes:
unzip (6.0-29+deb13u1) trixie-security; urgency=high
.
* Apply upstream fix for CAN-2026-2034440. Closes: #1142904.
(heap out-of-bounds read in EF_IZUNIX3 extra field handler)
* Apply upstream fix for CAN-2026-2034443. Closes: #1142905.
(stack out-of-bounds NUL write in EF_SMARTZIP handler)
* Apply upstream fix for CAN-2026-2034442. Closes: #1142906.
(heap buffer overflow WRITE in memextract() STORED path)
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unzip_6.0-29+deb13u1.debian.tar.xz
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Files:
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62b490407489521db863b523a7f86375 1376845 utils optional unzip_6.0.orig.tar.gz
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unzip_6.0-29+deb13u1.debian.tar.xz
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