UBUNTU-CVE-2026-33023

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Source
https://ubuntu.com/security/CVE-2026-33023
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-33023
Upstream
Published
2026-04-14T23:16:00Z
Modified
2026-05-20T16:25:23Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, when built with the --with-gdk-pixbuf2 option, a use-after-free vulnerability exists in load_with_gdkpixbuf() in loader.c. The cleanup path manually frees the sixel_frame_t object and its internal buffers without consulting the reference count, even though the object was created via the refcounted constructor sixel_frame_new() and exposed to the public callback. A callback that calls sixel_frame_ref(frame) to retain a logically valid reference will hold a dangling pointer after sixel_helper_load_image_file() returns, and any subsequent access to the frame or its fields triggers a use-after-free confirmed by AddressSanitizer. The root cause is a consistency failure between two cleanup strategies in the same codebase: sixel_frame_unref() is used in load_with_builtin() but raw free() is used in load_with_gdkpixbuf(). An attacker supplying a crafted image to any application built against libsixel with gdk-pixbuf2 support can trigger this reliably, potentially leading to information disclosure, memory corruption, or 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?arch=source&distro=xenial

Affected ranges

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

Affected versions

1.*
1.4.2-1
1.5.2-2

Ecosystem specific 

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

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:18.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel?arch=source&distro=bionic

Affected ranges

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

Affected versions

1.*
1.5.2-2
1.7.3-1

Ecosystem specific 

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

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:20.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel?arch=source&distro=focal

Affected ranges

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

Affected versions

1.*
1.8.2-1
1.8.2-2.1

Ecosystem specific 

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

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:22.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel?arch=source&distro=jammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown 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_name": "libsixel-bin",
            "binary_version": "1.10.3-3"
        },
        {
            "binary_name": "libsixel-examples",
            "binary_version": "1.10.3-3"
        },
        {
            "binary_name": "libsixel1",
            "binary_version": "1.10.3-3"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:24.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel?arch=source&distro=noble

Affected ranges

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

Affected versions

1.*
1.10.3-3
1.10.3-3build1

Ecosystem specific 

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

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:25.10
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel?arch=source&distro=questing

Affected ranges

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

Affected versions

1.*
1.10.5-1

Ecosystem specific 

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

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:26.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel?arch=source&distro=resolute

Affected ranges

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

Affected versions

1.*
1.10.5-1
1.10.5-1build1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_name": "libsixel-bin",
            "binary_version": "1.10.5-1build1"
        },
        {
            "binary_name": "libsixel-examples",
            "binary_version": "1.10.5-1build1"
        },
        {
            "binary_name": "libsixel1",
            "binary_version": "1.10.5-1build1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"