CVE-2026-33020
- Source
- https://cve.org/CVERecord?id=CVE-2026-33020
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-33020.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-33020
- Aliases
-
- GHSA-2xgm-4x47-2x2p
- Downstream
- Published
- 2026-04-14T21:53:00Z
- Modified
- 2026-10-21T02:56:47Z
- Severity
-
- 7.1 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H CVSS Calculator
- Summary
- libsixel: Integer Overflow in write_png_to_file() leads to Heap-based Buffer Overflow
- Details
-
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.
- Database specific
{ "cna_assigner": "GitHub_M", "cwe_ids": [ "CWE-122", "CWE-190" ], "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33020.json" }- References
Affected packages
Git / github.com/saitoha/libsixel
Affected ranges
- Type
- GIT
- Repo
- https://github.com/saitoha/libsixel
- Events
-
Introduced0 Unknown introduced commit / All previous commits are affectedFixed
- Database specific
-
Show details
{ "extracted_events": [ { "range": [ { "introduced": "0" }, { "fixed": "1.8.7-r1" } ], "source": "AFFECTED_FIELD", "strategy": "StringRangeExpression" }, { "original_tag": "v1.8.7-r1", "range": [ { "fixed": "6d628cf43548e1f2739cbb13afcc6e8257868db5" } ], "source": "REFERENCES_TAG" }, { "cpe": "cpe:2.3:a:saitoha:libsixel:*:*:*:*:*:*:*:*", "range": [ { "introduced": "0" }, { "fixed": "1.8.7-r1" } ], "source": "CPE_RANGE" } ] }