CVE catalog

CVE-2026-33020

Severity: High · CVSS 7.1CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
Published: Apr 14, 2026, 9:53:00 PM UTC
Source: [NVD] · [CVE record]
EPSS: 0.21% · Oct 25, 2026

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow which leads to a heap buffer overflow via sixel_frame_convert_to_rgb888() in frame.c, where allocation size and pointer offset computations for palettised images (PAL1, PAL2, PAL4) are performed using int arithmetic before casting to size_t. For images whose pixel count exceeds INT_MAX / 4, the overflow produces an undersized heap allocation for the conversion buffer and a negative pointer offset for the normalization sub-buffer, after which sixel_helper_normalize_pixelformat() writes the full image data starting from the invalid pointer, causing massive heap corruption confirmed by ASAN. An attacker providing a specially crafted large palettised PNG can corrupt the heap of the victim process, resulting in a reliable crash and potential arbitrary code execution. This issue has been fixed in version 1.8.7-r1.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	libsixel	sid	`1:1.8.7-r2-1`	fixed
Debian	libsixel	forky	`1:1.8.7-r2-1`	fixed
Debian	libsixel	trixie	`1.10.5-1`	vulnerable
Debian	libsixel	bookworm	`1.10.3-3`	vulnerable
Cpe	libsixel	Not reported	Not reported	vulnerable
Cpe	libsixel	Not reported	`1.8.7-r1`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	libsixel	source	sid	`1:1.8.7-r2-1`	not yet assigned	Not reported	[1136211]
Debian	libsixel	source	forky	`1:1.8.7-r2-1`	not yet assigned	Not reported	[1136211]
Debian	libsixel	source	trixie	`(unfixed)`	not yet assigned	Not reported	[1136211]
Debian	libsixel	source	bookworm	`(unfixed)`	not yet assigned	Not reported	[1136211]
Cpe	libsixel	cpe	Not reported	`1.8.7-r1`	Not reported	Not reported	Not reported

[Debian bug #1136211]

Notes

[trixie] libsixel: Minor issue [bookworm] libsixel: Minor issue

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[libsixel1]Affected
Source package: [libsixel]
Details (2)
- 1.10.3-3 · amd64 · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12
- 1.10.3-3 · arm64 · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12
[libsixel-bin]Affected
Source package: [libsixel]
Details (2)
- 1.10.3-3 · amd64 · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12
- 1.10.3-3 · arm64 · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12
[libsixel-dev]Affected
Source package: [libsixel]
Details (2)
- 1.10.3-3 · amd64 · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12
- 1.10.3-3 · arm64 · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12
[libsixel-examples]Affected
Source package: [libsixel]
Details (2)
- 1.10.3-3 · all · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12
- 1.10.3-3 · all · bookworm
  Affected
  nvd · libsixel · debian · bookworm; nvd · libsixel · debian · 12

[Debian 13 (Trixie)]

[libsixel1]Affected
Source package: [libsixel]
Details (2)
- 1.10.5-1 · amd64 · trixie
  Affected
  nvd · libsixel · debian · 13
- 1.10.5-1 · arm64 · trixie
  Affected
  nvd · libsixel · debian · 13
[libsixel-bin]Affected
Source package: [libsixel]
Details (2)
- 1.10.5-1 · amd64 · trixie
  Affected
  nvd · libsixel · debian · 13
- 1.10.5-1 · arm64 · trixie
  Affected
  nvd · libsixel · debian · 13
[libsixel-dev]Affected
Source package: [libsixel]
Details (2)
- 1.10.5-1 · amd64 · trixie
  Affected
  nvd · libsixel · debian · 13
- 1.10.5-1 · arm64 · trixie
  Affected
  nvd · libsixel · debian · 13
[libsixel-examples]Affected
Source package: [libsixel]
Details (2)
- 1.10.5-1 · all · trixie
  Affected
  nvd · libsixel · debian · 13
- 1.10.5-1 · all · trixie
  Affected
  nvd · libsixel · debian · 13

Observed: Oct 23, 2026, 10:34:17 PM UTC

References

[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]