CVE-2026-44637: libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel

Routine

HIGH 7.1UPGRADE

CVE-2026-44637 is a high-severity flaw (CVSS 7.1) affecting libsixel. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. context->pos_x grows by repeat_count on every sixel character with no upper bound check. Once pos_x approaches INT_MAX, the expression "pos_x + repeat_count" used to size the image buffer overflows signed int. D

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.1 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 95%)
CISA exploited list	No
Weakness	CWE-190, CWE-787
Published	2026-05-14
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: saitoha

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-14 20:17 UTCPublished CVE record published
2026-10-26 14:10 UTCUpdated Record last modified

saitoha libsixel UPGRADE

Affected: >= 0.11.0 and < 1.8.7-r2

Fixed in: 1.8.7-r2

Safe to downgrade to: a release before 0.11.0

1. Check installed version

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

2. UPGRADE to 1.8.7-r2 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libsixel

Note

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

3. If no update is available yet, DOWNGRADE to a release before 0.11.0 (Debian / Ubuntu)

apt-cache madison libsixel sudo apt install libsixel=<VERSION_BEFORE_0.11.0> sudo apt-mark hold libsixel

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list libsixel sudo dnf downgrade libsixel-<VERSION_BEFORE_0.11.0> sudo dnf versionlock add libsixel

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.

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-2026-44637?

libsixel: upgrade to 1.8.7-r2. Exact commands for each OS are on this page.

Is CVE-2026-44637 being exploited?

CVE-2026-44637 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-2026-44637 affect?

CVE-2026-44637 affects libsixel. Severity is high (CVSS 7.1). libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. c

How urgent is CVE-2026-44637?

Priority 31/100. High severity; Public exploit reference

Related CVEs

CVE-2026-44636 HIGH 7.4 UPGRADE libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel
CVE-2026-44638 LOW 2.5 UPGRADE libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel

References

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