UBUNTU-CVE-2026-33020

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Source
https://ubuntu.com/security/CVE-2026-33020
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33020.json
JSON Data
https://api.test.osv.dev/v1/vulns/UBUNTU-CVE-2026-33020
Upstream
  • CVE-2026-33020
Published
2026-04-14T22:16:00Z
Modified
2026-04-16T11:04:58.926050Z
Severity
  • 7.1 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow which leads to a heap buffer overflow via sixelframeconverttorgb888() in frame.c, where allocation size and pointer offset computations for palettised images (PAL1, PAL2, PAL4) are performed using int arithmetic before casting to sizet. For images whose pixel count exceeds INTMAX / 4, the overflow produces an undersized heap allocation for the conversion buffer and a negative pointer offset for the normalization sub-buffer, after which sixelhelpernormalize_pixelformat() writes the full image data starting from the invalid pointer, causing massive heap corruption confirmed by ASAN. An attacker providing a specially crafted large palettised PNG can corrupt the heap of the victim process, resulting in a reliable crash and potential arbitrary code execution. This issue has been fixed in version 1.8.7-r1.

References

Affected packages

Ubuntu:16.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.5.2-2?arch=source&distro=xenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.4.2-1
1.5.2-2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.5.2-2",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.5.2-2",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.5.2-2",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33020.json"
Ubuntu:18.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.7.3-1?arch=source&distro=bionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.5.2-2
1.7.3-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33020.json"
Ubuntu:20.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.8.2-2.1?arch=source&distro=focal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.2-1
1.8.2-2.1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33020.json"
Ubuntu:22.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.10.3-3?arch=source&distro=jammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.6-2
1.10.3-2
1.10.3-3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33020.json"
Ubuntu:24.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.10.3-3build1?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.10.3-3
1.10.3-3build1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33020.json"
Ubuntu:25.10
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.10.5-1?arch=source&distro=questing

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.10.5-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33020.json"