High
libsixel — security advisory
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow leading to an out-of-bounds heap read in the --crop option handling of img2sixel, where positive coordinates up to INT_MAX are accepted without overflow-safe bounds checking. In sixel_encoder_do_clip(), the expression clip_w + clip_x overflows to a large negative value when clip_x is INT_MAX, causing the bounds guard to be skipped entirely, and the unclamped coordinate is passed through sixel_frame_clip() to clip(), which computes a source pointer far beyond the image buffer and passes it to memmove(). An attacker supplying a specially crafted crop argument with any valid image can trigger an out-of-bounds read in the heap, resulting in a reliable crash and potential information disclosure. This issue has been fixed in version 1.8.7-r1.
- Products
- libsixel
- Affected versions
- 1.10.3-2, 1.10.3-3, 1.10.3-3build1, 1.10.5-1, 1.10.5-1build1, 1.4.2-1, 1.5.2-2, 1.7.3-1, 1.8.2-1, 1.8.2-2.1, 1.8.6-2, 1:1.8.7-r2-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-33019
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:59 UTC · Revision 1
Source evidence
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow leading to an out-of-bounds heap read in the --crop option handling of img2sixel, where positive coordinates up to INT_MAX are accepted without overflow-safe bounds checking. In sixel_encoder_do_clip(), the expression clip_w + clip_x overflows to a large negative value when clip_x is INT_MAX, causing the bounds guard to be skipped entirely, and the unclamped coordinate is passed through sixel_frame_clip() to clip(), which computes a source pointer far beyond the image buffer and passes it to memmove(). An attacker supplying a specially crafted crop argument with any valid image can trigger an out-of-bounds read in the heap, resulting in a reliable crash and potential information disclosure. This issue has been fixed in version 1.8.7-r1.
osv:UBUNTU-CVE-2026-33019
libsixel
Fixed versions: Not specified
libsixel
Fixed versions: Not specified
libsixel
Fixed versions: Not specified
libsixel
Fixed versions: Not specified
libsixel
Fixed versions: Not specified
libsixel
Fixed versions: Not specified
libsixel
Fixed versions: Not specified
libsixel
Fixed versions: Not specified
Complete source record
{
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"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-33019",
"method": "structured",
"payload": {
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"title": "UBUNTU-CVE-2026-33019",
"summary": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow leading to an out-of-bounds heap read in the --crop option handling of img2sixel, where positive coordinates up to INT_MAX are accepted without overflow-safe bounds checking. In sixel_encoder_do_clip(), the expression clip_w + clip_x overflows to a large negative value when clip_x is INT_MAX, causing the bounds guard to be skipped entirely, and the unclamped coordinate is passed through sixel_frame_clip() to clip(), which computes a source pointer far beyond the image buffer and passes it to memmove(). An attacker supplying a specially crafted crop argument with any valid image can trigger an out-of-bounds read in the heap, resulting in a reliable crash and potential information disclosure. This issue has been fixed in version 1.8.7-r1.",
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"modified": "2026-10-17T12:59:58.469318869Z",
"provider": "osv",
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"references": [
"https://ubuntu.com/security/CVE-2026-33019",
"https://www.cve.org/CVERecord?id=CVE-2026-33019",
"https://github.com/saitoha/libsixel/security/advisories/GHSA-c854-ffg9-g72c",
"https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1"
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"source_id": "core-osv",
"document_id": 360049,
"published_at": "2026-04-14T22:16:00+00:00"
}