UBUNTU-CVE-2026-33021

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Source
https://ubuntu.com/security/CVE-2026-33021
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33021.json
JSON Data
https://api.test.osv.dev/v1/vulns/UBUNTU-CVE-2026-33021
Upstream
  • CVE-2026-33021
Published
2026-04-14T23:16:00Z
Modified
2026-04-16T11:04:39.801964Z
Severity
  • 7.3 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/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 a use-after-free vulnerability in sixelencoderencodebytes() because sixelframeinit() stores the caller-owned pixel buffer pointer directly in frame->pixels without making a defensive copy. When a resize operation is triggered, sixelframeconvertto_rgb888() unconditionally frees this caller-owned buffer and replaces it with a new internal allocation, leaving the caller with a dangling pointer. Any subsequent access to the original buffer by the caller constitutes a use-after-free, confirmed by AddressSanitizer. An attacker who controls incoming frames can trigger this bug repeatedly and predictably, resulting in a reliable crash with potential for 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-2026-33021.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-2026-33021.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-2026-33021.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-2026-33021.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-2026-33021.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-2026-33021.json"