CVE-2018-18584: In mspack/cab.h in libmspack before 0.8alpha and cabextract before 1.8, the CAB block input buffer is one byte

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MEDIUM 6.5WATCHLISTUPGRADEDOWNGRADEMITIGATE

CVE-2018-18584 is a medium-severity flaw (CVSS 6.5) affecting cabextract, libmspack, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In mspack/cab.h in libmspack before 0.8alpha and cabextract before 1.8, the CAB block input buffer is one byte too small for the maximal Quantum block, leading to an out-of-bounds write.

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	2.7% (top 14%)
CISA exploited list	No
Weakness	CWE-787
Published	2018-10-23
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: cabextract project · canonical · debian · libmspack project · redhat · suse

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-10-23 02:29 UTCPublished CVE record published
2026-06-17 01:47 UTCUpdated Record last modified

cabextract project cabextract UPGRADE

Affected: < 1.8

Fixed in: 1.8

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cabextract || rpm -q cabextract || cabextract --version

2. UPGRADE to 1.8 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cabextract

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cabextract

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

libmspack project libmspack DOWNGRADE

Affected: 0.3 alpha · 0.4 alpha · 0.5 alpha · 0.6 alpha · 0.7 alpha · 0.7.1 alpha

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.3

1. Check installed version

apt-cache policy libmspack || rpm -q libmspack || libmspack --version

2. No fixed release: DOWNGRADE to a release before 0.3 (Debian / Ubuntu)

apt-cache madison libmspack sudo apt install libmspack=<VERSION_BEFORE_0.3> sudo apt-mark hold libmspack

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list libmspack sudo dnf downgrade libmspack-<VERSION_BEFORE_0.3> sudo dnf versionlock add libmspack

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

debian debian linux MITIGATE

Affected: 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

canonical ubuntu linux MITIGATE

Affected: 12.04 · 14.04 · 16.04 · 18.04 · 18.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 12.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

suse linux enterprise server MITIGATE

Affected: 11 sp3 · 12 ga · 12 sp1 · 12 sp2

Fixed in: no fixed release known

Safe to downgrade to: a release before 11

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2018-18584?

cabextract: upgrade to 1.8; libmspack: downgrade or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2018-18584 being exploited?

CVE-2018-18584 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2018-18584 affect?

CVE-2018-18584 affects cabextract, libmspack, debian linux. Severity is medium (CVSS 6.5). In mspack/cab.h in libmspack before 0.8alpha and cabextract before 1.8, the CAB block input buffer is one byte too small for the maximal Quantum block, leading to an out-of-bounds write.

How urgent is CVE-2018-18584?

Priority 49/100. On your watchlist

Software pages

Ubuntu vulnerabilities · Debian vulnerabilities

Related CVEs

CVE-2018-14682 HIGH 8.8 DOWNGRADE UPGRADE An issue was discovered in mspack/chmd.c in libmspack before 0.7alpha
CVE-2018-14681 HIGH 8.8 DOWNGRADE UPGRADE An issue was discovered in kwajd_read_headers in mspack/kwajd.c in libmspack before 0.7alpha
CVE-2018-14680 MEDIUM 6.5 DOWNGRADE UPGRADE An issue was discovered in mspack/chmd.c in libmspack before 0.7alpha
CVE-2018-14679 MEDIUM 6.5 DOWNGRADE UPGRADE An issue was discovered in mspack/chmd.c in libmspack before 0.7alpha
CVE-2015-2060 MEDIUM 5.3 UPGRADE cabextract before 1.6 does not properly check for leading slashes when extracting files, which allows remote a

References

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