CVE-2026-117556
zchunk before 1.5.5 Heap Out-of-Bounds Read via read_preface()
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Passive
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
zchunk before 1.5.5 Heap Out-of-Bounds Read via read_preface()
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
CVE-2026-117556- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L - Weakness
- CWE-125
- Updated
- 2026-11-02
EUVDEUVD-2026-110834
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
EUVD-2026-110834- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-xcf7-q4j8-4wvv
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib...
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
GHSA-xcf7-q4j8-4wvv- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L - Weakness
- CWE-125
- Updated
- 2026-11-02
NVD
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
CVE-2026-117556- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L - Weakness
- CWE-125
- Updated
- 2026-11-02
OSV
zchunk before 1.5.5 Heap Out-of-Bounds Read via read_preface()
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
CVE-2026-117556- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - Weakness
- CWE-125
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-117556
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
DEBIAN-CVE-2026-117556- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-117556
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
UBUNTU-CVE-2026-117556- CVSS 4.0
- 5.3 Medium
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
OSVAZL-111188 No score
CVE-2026-117556 affecting package zchunk for versions less than 1.5.5-1
zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
- Record
AZL-111188- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
zchunkAzure Linux:3 |
before 1.5.5-1 | 1.5.5-1 |
zchunkDebian:12 |
All versions, plus listed versions 1.2.3+ds1-21.3.0+ds1-0.11.3.1+ds1-11.3.1+ds1-1~bpo12+11.3.2+ds1-1 Show 7 moreShow less1.4.0+ds1-11.5.1+ds1-11.5.1+ds1-1~bpo12+11.5.2+ds1-11.5.2+ds1-21.5.3+ds1-11.5.3+ds1-2 |
None known |
zchunkDebian:13 |
All versions, plus listed versions 1.5.1+ds1-11.5.2+ds1-11.5.2+ds1-21.5.3+ds1-11.5.3+ds1-2 |
None known |
zchunkDebian:14 |
All versions, plus listed versions 1.5.1+ds1-11.5.2+ds1-11.5.2+ds1-21.5.3+ds1-11.5.3+ds1-2 |
None known |
zchunkUbuntu:22.04:LTS |
All versions, plus listed versions 1.1.9+ds1-11.1.16+ds1-1 |
None known |
zchunkUbuntu:24.04:LTS |
All versions, plus listed versions 1.3.1+ds1-11.3.2+ds1-11.3.2+ds1-1build11.3.2+ds1-1build2 |
None known |
zchunkUbuntu:26.10 |
All versions, plus listed versions 1.5.2+ds1-21.5.3+ds1-1 |
None known |
zchunkUbuntu:26.04:LTS |
All versions, plus listed versions 1.5.1+ds1-11.5.2+ds1-11.5.2+ds1-2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-117556 is a medium vulnerability (CVSS 5.3) in Microsoft Zchunk, published October 27, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.33%, the 26th percentile. Fixed in zchunk 1.5.5-1.
References
github.com/zchunk/zchunk/issues/119
vulncheck.com/advisories/zchunk-before-1.5.5-heap-out-of-bounds-read-via-read-preface