CVE-2026-44636: libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel

Routine

HIGH 7.4UPGRADE

CVE-2026-44636 is a high-severity flaw (CVSS 7.4) 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, signed integer overflow in sixel_encode_highcolor's allocation size calculation can lead to a heap buffer overflow. The public sixel_encode entry point validates only that width and height are greater than zero, with no upper bound. width and height are multiplied as plain int when computing the allocation size for paletted_pixels and normalized_pixe

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.4 (High)
Attack vector	Local
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.1% (top 99%)
CISA exploited list	No
Weakness	CWE-122, CWE-190
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: >= 1.4.4 and < 1.8.7-r2

Fixed in: 1.8.7-r2

Safe to downgrade to: a release before 1.4.4

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 1.4.4 (Debian / Ubuntu)

apt-cache madison libsixel sudo apt install libsixel=<VERSION_BEFORE_1.4.4> 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_1.4.4> 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-2026-44636?

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

Is CVE-2026-44636 being exploited?

CVE-2026-44636 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-2026-44636 affect?

CVE-2026-44636 affects libsixel. Severity is high (CVSS 7.4). libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, signed integer overflow in sixel_encode_highcolor's allocation size calculation can lead to a heap buffer overflow. The public sixel_encode en

How urgent is CVE-2026-44636?

Priority 26/100. High severity

Related CVEs

CVE-2026-44637 HIGH 7.1 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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