Medium
kitty — security advisory
Out-of-bounds Write in the natural width branch of the text sizing protocol in kitty from 0.40.0 before 0.49.0 allows a program writing to the terminal to write past the end of a fixed-size buffer, because screen_handle_multicell_command() in kitty/screen.c appends each codepoint of a grapheme cluster with lc.chars[lc.count++] = ch without any capacity check, while lc is declared by the RAII_ListOfChars macro as a four-element char_type array in the function's stack frame, so an OSC 66 escape code whose payload carries a grapheme cluster longer than four codepoints writes beyond that buffer, one 32-bit value per additional codepoint, in the order the codepoints appear. Where the cluster is preceded in the same payload by a sequence that causes an intermediate flush, the buffer is first migrated to the heap by ensure_space_for_chars() and the write occurs past the heap allocation instead. This results in termination of the kitty process and therefore of all its windows, tabs and child processes.
- Products
- kitty
- Affected versions
- 0.14.3-1, 0.14.4-1, 0.14.6-1, 0.15.0-1, 0.15.0-1build1, 0.15.0-1ubuntu0.2, 0.15.0-1ubuntu0.2+esm1, 0.19.3-1, 0.21.2-1, 0.21.2-1build1, 0.21.2-1ubuntu0.22.04.1, 0.21.2-1ubuntu0.22.04.1+esm1, 0.26.5-3ubuntu2, 0.26.5-5ubuntu1, 0.31.0-3, 0.31.0-4, 0.32.2-1, 0.32.2-1build2, 0.32.2-1build3, 0.32.2-1ubuntu0.1, 0.32.2-1ubuntu0.2, 0.32.2-1ubuntu0.3, 0.32.2-1ubuntu0.4, 0.32.2-1ubuntu0.4+esm1, 0.32.2-1ubuntu0.4+esm2, 0.41.1-2, 0.43.1-1, 0.44.0-1, 0.45.0-1, 0.45.0-1build1, 0.45.0-1ubuntu0.1~esm1, 0.45.0-1ubuntu0.1~esm2, 0.47.0-3, 0.47.4-1, 0.48.2-1.1ubuntu1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-80431
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:20 UTC · Revision 1
Source evidence
Out-of-bounds Write in the natural width branch of the text sizing protocol in kitty from 0.40.0 before 0.49.0 allows a program writing to the terminal to write past the end of a fixed-size buffer, because screen_handle_multicell_command() in kitty/screen.c appends each codepoint of a grapheme cluster with lc.chars[lc.count++] = ch without any capacity check, while lc is declared by the RAII_ListOfChars macro as a four-element char_type array in the function's stack frame, so an OSC 66 escape code whose payload carries a grapheme cluster longer than four codepoints writes beyond that buffer, one 32-bit value per additional codepoint, in the order the codepoints appear. Where the cluster is preceded in the same payload by a sequence that causes an intermediate flush, the buffer is first migrated to the heap by ensure_space_for_chars() and the write occurs past the heap allocation instead. This results in termination of the kitty process and therefore of all its windows, tabs and child processes.
osv:UBUNTU-CVE-2026-80431
kitty
Fixed versions: Not specified
kitty
Fixed versions: Not specified
kitty
Fixed versions: Not specified
kitty
Fixed versions: Not specified
kitty
Fixed versions: Not specified
Complete source record
{
"id": "dd887a0f9439cbe476ba035f96057104184437818e254dbb71b553c4374c3a4f",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-80431",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-80431",
"summary": "Out-of-bounds Write in the natural width branch of the text sizing protocol in kitty from 0.40.0 before 0.49.0 allows a program writing to the terminal to write past the end of a fixed-size buffer, because screen_handle_multicell_command() in kitty/screen.c appends each codepoint of a grapheme cluster with lc.chars[lc.count++] = ch without any capacity check, while lc is declared by the RAII_ListOfChars macro as a four-element char_type array in the function's stack frame, so an OSC 66 escape code whose payload carries a grapheme cluster longer than four codepoints writes beyond that buffer, one 32-bit value per additional codepoint, in the order the codepoints appear. Where the cluster is preceded in the same payload by a sequence that causes an intermediate flush, the buffer is first migrated to the heap by ensure_space_for_chars() and the write occurs past the heap allocation instead. This results in termination of the kitty process and therefore of all its windows, tabs and child processes.",
"evidence": "osv:UBUNTU-CVE-2026-80431",
"products": [
{
"name": {
"value": "kitty",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
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"affected_versions": [
{
"value": "0.14.3-1",
"evidence": "/affected/0/versions"
},
{
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"evidence": "/affected/0/versions"
},
{
"value": "0.14.6-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.15.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "0.15.0-1build1",
"evidence": "/affected/0/versions"
},
{
"value": "0.15.0-1ubuntu0.2",
"evidence": "/affected/0/versions"
},
{
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"evidence": "/affected/0/versions"
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{
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{
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{
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{
"value": "0.21.2-1ubuntu0.22.04.1",
"evidence": "/affected/1/versions"
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{
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"evidence": "/affected/1/versions"
}
]
},
{
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},
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"affected_versions": [
{
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"evidence": "/affected/2/versions"
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{
"value": "0.26.5-5ubuntu1",
"evidence": "/affected/2/versions"
},
{
"value": "0.31.0-3",
"evidence": "/affected/2/versions"
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{
"value": "0.31.0-4",
"evidence": "/affected/2/versions"
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{
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{
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"evidence": "/affected/2/versions"
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{
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"evidence": "/affected/2/versions"
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{
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"evidence": "/affected/2/versions"
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{
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{
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"evidence": "/affected/2/versions"
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{
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"evidence": "/affected/2/versions"
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{
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"evidence": "/affected/2/versions"
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{
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},
{
"name": {
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"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.45.0-1build1",
"evidence": "/affected/3/versions"
},
{
"value": "0.47.0-3",
"evidence": "/affected/3/versions"
},
{
"value": "0.47.4-1",
"evidence": "/affected/3/versions"
},
{
"value": "0.48.2-1.1ubuntu1",
"evidence": "/affected/3/versions"
}
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},
{
"name": {
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"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "0.41.1-2",
"evidence": "/affected/4/versions"
},
{
"value": "0.43.1-1",
"evidence": "/affected/4/versions"
},
{
"value": "0.44.0-1",
"evidence": "/affected/4/versions"
},
{
"value": "0.45.0-1",
"evidence": "/affected/4/versions"
},
{
"value": "0.45.0-1build1",
"evidence": "/affected/4/versions"
},
{
"value": "0.45.0-1ubuntu0.1~esm1",
"evidence": "/affected/4/versions"
},
{
"value": "0.45.0-1ubuntu0.1~esm2",
"evidence": "/affected/4/versions"
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}
],
"severity": "medium",
"structured": {
"id": "UBUNTU-CVE-2026-80431",
"aliases": [
"UBUNTU-CVE-2026-80431"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "kitty",
"purl": "pkg:deb/ubuntu/kitty?arch=source&distro=esm-apps%2Ffocal",
"ecosystem": "Ubuntu:Pro:20.04:LTS"
},
"versions": [
"0.14.3-1",
"0.14.4-1",
"0.14.6-1",
"0.15.0-1",
"0.15.0-1build1",
"0.15.0-1ubuntu0.2",
"0.15.0-1ubuntu0.2+esm1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-80431.json"
},
"ecosystem_specific": {
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"binary_version": "0.15.0-1ubuntu0.2+esm1"
},
{
"binary_name": "kitty-terminfo",
"binary_version": "0.15.0-1ubuntu0.2+esm1"
}
]
}
},
{
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"package": {
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"purl": "pkg:deb/ubuntu/kitty?arch=source&distro=esm-apps%2Fjammy",
"ecosystem": "Ubuntu:Pro:22.04:LTS"
},
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"0.21.2-1",
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},
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}
},
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},
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"0.32.2-1",
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"0.32.2-1build3",
"0.32.2-1ubuntu0.1",
"0.32.2-1ubuntu0.2",
"0.32.2-1ubuntu0.3",
"0.32.2-1ubuntu0.4",
"0.32.2-1ubuntu0.4+esm1",
"0.32.2-1ubuntu0.4+esm2"
],
"database_specific": {
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},
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},
{
"binary_name": "kitty-shell-integration",
"binary_version": "0.32.2-1ubuntu0.4+esm2"
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},
"versions": [
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"database_specific": {
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},
"ecosystem_specific": {
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{
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},
{
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}
],
"modified": "2026-10-17T13:01:10.480065892Z",
"provider": "osv",
"upstream": [
"CVE-2026-80431"
],
"references": [
"https://ubuntu.com/security/CVE-2026-80431",
"https://www.cve.org/CVERecord?id=CVE-2026-80431",
"https://github.com/kovidgoyal/kitty/commit/7d2fbaadcc2b1eeeef89bd875ec622b42362574b",
"https://github.com/kovidgoyal/kitty/releases/tag/v0.49.0",
"https://secur0.com/en/cna/cve-list/cve-2026-80431-kitty-text-sizing-out-of-bounds-write"
]
},
"related_cves": [
{
"value": "CVE-2026-80431",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 361131,
"published_at": "2026-09-25T14:17:00+00:00"
}