CVE-2021-45340: In Libsixel prior to and including v1.10.3, a NULL pointer dereference in the stb_image.h component of libsixe

Q: How do I fix CVE-2021-45340?

libsixel: upgrade to newer than 1.10.3. Exact commands for each OS are on this page.

Q: Is CVE-2021-45340 being exploited?

CVE-2021-45340 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-45340 affect?

CVE-2021-45340 affects libsixel. Severity is medium (CVSS 6.5). In Libsixel prior to and including v1.10.3, a NULL pointer dereference in the stb_image.h component of libsixel allows attackers to cause a denial of service (DOS) via a crafted PICT file.

Q: How urgent is CVE-2021-45340?

Priority 43/100. Public exploit reference

This month

MEDIUM 6.5UPGRADE

CVE-2021-45340 is a medium-severity flaw (CVSS 6.5) affecting libsixel. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In Libsixel prior to and including v1.10.3, a NULL pointer dereference in the stb_image.h component of libsixel allows attackers to cause a denial of service (DOS) via a crafted PICT file.

Why this priority

Public exploit reference

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	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-476
Published	2022-01-25
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: libsixel

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

Am I affected?

Timeline

2022-01-25 12:15 UTCPublished CVE record published
2026-06-17 04:13 UTCUpdated Record last modified

libsixel libsixel UPGRADE

Affected: <= 1.10.3

Fixed in: newer than 1.10.3

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.10.3 (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.

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-2021-45340?

libsixel: upgrade to newer than 1.10.3. Exact commands for each OS are on this page.

Is CVE-2021-45340 being exploited?

CVE-2021-45340 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-2021-45340 affect?

CVE-2021-45340 affects libsixel. Severity is medium (CVSS 6.5). In Libsixel prior to and including v1.10.3, a NULL pointer dereference in the stb_image.h component of libsixel allows attackers to cause a denial of service (DOS) via a crafted PICT file.

How urgent is CVE-2021-45340?

Priority 43/100. Public exploit reference

Related CVEs

CVE-2026-44637 HIGH 7.1 UPGRADE libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel
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
CVE-2026-33023 HIGH 7.8 UPGRADE libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel
CVE-2026-33021 HIGH 7.3 UPGRADE libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel

References

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