{"id":"UBUNTU-CVE-2026-44637","details":"libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From  to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. context-\u003epos_x grows by repeat_count on every sixel character with no upper bound check. Once pos_x approaches INT_MAX, the expression \"pos_x + repeat_count\" used to size the image buffer overflows signed int. Depending on how the overflow wraps, the resize check that should reject oversized buffers can be bypassed, after which a subsequent write computes a large attacker-influenced offset into image-\u003edata and writes past the allocation. Reachable from any caller that decodes attacker-supplied SIXEL data, including img2sixel. This vulnerability is fixed in 1.8.7-r2.","modified":"2026-05-20T22:03:08.765892827Z","published":"2026-05-14T20:17:00Z","upstream":["CVE-2026-44637"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-44637"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-44637"},{"type":"REPORT","url":"https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghv"}],"affected":[{"package":{"name":"libsixel","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/libsixel?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["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":"libsixel1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-44637.json"}},{"package":{"name":"libsixel","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/libsixel?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["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-2026-44637.json"}},{"package":{"name":"libsixel","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/libsixel?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["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_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-2026-44637.json"}},{"package":{"name":"libsixel","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/libsixel?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["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_version":"1.10.3-3","binary_name":"libsixel-examples"},{"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-2026-44637.json"}},{"package":{"name":"libsixel","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/libsixel?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.3-3","1.10.3-3build1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.10.3-3build1","binary_name":"libsixel-bin"},{"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-2026-44637.json"}},{"package":{"name":"libsixel","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/libsixel?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["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_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-2026-44637.json"}},{"package":{"name":"libsixel","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/libsixel?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.5-1","1.10.5-1build1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.10.5-1build1","binary_name":"libsixel-bin"},{"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-2026-44637.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}