Your message dated Tue, 18 Aug 2026 21:48:32 +0000
with message-id <[email protected]>
and subject line Bug#1142906: fixed in unzip 6.0-29+deb13u1
has caused the Debian Bug report #1142906,
regarding unzip: heap buffer overflow WRITE in memextract() STORED path
[CAN-2026-2034442]
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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--
1142906: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1142906
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 heap buffer overflow WRITE in the
memextract() function (extract.c) when processing STORED-compressed
VMS extra field blocks. The allocation uses the declared uncompressed
size (usiz), but the STORED copy path uses the compressed data length
(G.incnt, derived from csiz). When csiz > usiz, memcpy writes past
the heap buffer.
CAN: CAN-2026-2034442 (pending assignment from MITRE)
CWE: CWE-122 (Heap-based Buffer Overflow)
CVSS: 8.5 High
ROOT CAUSE:
In extract_izvms_block() (extract.c, line 2645):
usiz = (cmptype == EB_IZVMS_BCSTOR ?
csiz : makeword(ebdata+EB_IZVMS_UCSIZ));
...
ucdata = (uch *)malloc(MAX(needlen, usiz)); // alloc'd with usiz
For the EB_IZVMS_BCDEFL case, memextract() is called:
memextract(__G__ ucdata, (ulg)usiz,
ebdata+EB_IZVMS_HLEN, (ulg)csiz);
Inside memextract() (extract.c, line 2523), the STORED path:
G.inptr = (uch *)src + (2 + 4);
G.incnt = (int)(G.csize = (long)(srcsize - (2 + 4))); // from csiz
...
case STORED:
memcpy((char *)tgt, (char *)G.inptr, (extent)G.incnt);
The memcpy uses G.incnt (derived from srcsize/csiz) as the copy length,
but tgt is only usiz bytes. The method field inside the extra field data
is attacker-controlled — a crafted EF_IZVMS block declares
cmptype=EB_IZVMS_BCDEFL (to reach memextract) with a method byte of
STORED=0 inside the block data, usiz=16, and csiz=86. The memcpy then
copies 80 bytes into a 16-byte buffer.
TRIGGER: unzip -a -o poc.zip where poc.zip has version_made_by=0x0214
(VMS host system) and contains a crafted EF_IZVMS extra field with
the above geometry.
ASAN OUTPUT:
==8==ERROR: AddressSanitizer: heap-buffer-overflow on address
0xffff98400740 at pc 0xaaaacd723054
WRITE of size 80 at 0xffff98400740 thread T0
#0 __asan_memcpy
#1 memextract /build/unzip-6.0/extract.c:2523:13
#2 extract_izvms_block /build/unzip-6.0/extract.c:2660:13
#3 is_vms_varlen_txt /build/unzip-6.0/fileio.c:1181:32
#4 flush /build/unzip-6.0/fileio.c:896:17
#5 extract_or_test_member /build/unzip-6.0/extract.c:1921:21
0xffff98400740 is located 0 bytes to the right of 16-byte region
[0xffff98400730,0xffff98400740)
allocated by thread T0 here:
#1 extract_izvms_block /build/unzip-6.0/extract.c:2645:26
IMPACT: Heap buffer overflow WRITE with attacker-controlled length
(csiz - usiz - 6 bytes written past the allocation). This is a
write primitive — potential for code execution depending on heap
layout. Triggered during normal extraction of a crafted ZIP file.
SUGGESTED FIX (in memextract, STORED case):
case STORED:
+ if ((extent)G.incnt > tgtsize) {
+ error = PK_ERR;
+ break;
+ }
memcpy((char *)tgt, (char *)G.inptr, (extent)G.incnt);
Or equivalently, validate in extract_izvms_block() that csiz <= usiz + 6
before calling memextract with cmptype BCDEFL.
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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unzip_6.0-29+deb13u1_source.buildinfo
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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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unzip_6.0-29+deb13u1_source.buildinfo
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