Signal is active with 1 mentions in latest observed window
Recommended action window: Monitor and triage in normal cycle
NVD description
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.
Priority
LOW
Exploitation
NONE
PoC
YES
Patch
AVAILABLE
Momentum
STABLE
If you run products in this scope, you should treat this CVE as relevant to your environment.
| Date | Total | Labels |
|---|
| 2026-04-15 | 2 | Disclosure2 |
| 2026-07-31 | 1 | Patch1 |
🚨 HIGH: CVE-2026-33020 (CVSS 7.1) libsixel ≤1.8.7 - Integer overflow → heap buffer overflow via crafted PNG. Potential RCE. ✅ Fixed in 1.8.7-r1 #CVE #Vulnerability #PatchNow #ThreatIntel https://t.co/BeXwrKYhBJ
Post summary
The tweet announces CVE‑2026‑33020, detailing an integer overflow in libsixel that can lead to RCE, and confirms that the issue is fixed in version 1.8.7‑r1, with no evidence of active exploitation or PoC.
CVE-2026-33020 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 overf… https://www.cve.org/CVERecord?id=CVE-2026-33020
Post summary
The post announces CVE‑2026‑33020, an integer overflow in libsixel (v1.8.7 and earlier) that causes a heap buffer overflow.
CVE-2026-33020 Integer Overflow and Heap Buffer Overflow in libsixel Versions 1.8.7 and Prior https://vulmon.com/vulnerabilitydetails?qid=CVE-2026-33020
Post summary
Issues a disclosure of integer and heap buffer overflow vulnerabilities affecting libsixel versions up to 1.8.7, with no further exploit or patch details.
1 of 1 entries
| Part | Vendor | Product | Version | Target SW | Target HW |
|---|---|---|---|---|---|
| App | saitoha | libsixel | - | - | - |