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CVE-2026-33019— libsixel: Integer overflow leads to Out-of-bounds Read in img2sixel

Quick assessment

Affected
saitoha libsixel
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

libsixel是Hayaki Saito个人开发者的一个为DEC SIXEL图形和其他转换器程序提供编码/解码实现的软件包。 libsixel 1.8.7及之前版本存在输入验证错误漏洞，该漏洞源于img2sixel的--crop选项处理存在整数溢出，可能导致越界堆读取，造成崩溃或信息泄露。

CVSS 7.1 · High EPSS 0.26% · P17

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution
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I. Basic Information for CVE-2026-33019

Vulnerability Information
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Vulnerability Title
libsixel: Integer overflow leads to Out-of-bounds Read in img2sixel
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
Source: CVE Program / CVE List V5
Vulnerability Title
libsixel 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
libsixel是Hayaki Saito个人开发者的一个为DEC SIXEL图形和其他转换器程序提供编码/解码实现的软件包。 libsixel 1.8.7及之前版本存在输入验证错误漏洞，该漏洞源于img2sixel的--crop选项处理存在整数溢出，可能导致越界堆读取，造成崩溃或信息泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
saitoha libsixel < 1.8.7-r1 -

II. Public POCs for CVE-2026-33019

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III. Intelligence Information for CVE-2026-33019

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Same Patch Batch · saitoha · 2026-04-14 · 5 CVEs total

CVE-2026-33023 7.8 HIGH libsixel: Use-after-free in load_with_gdkpixbuf()
CVE-2026-33021 7.3 HIGH libsixel: Use-after-free in sixel_encoder_encode_bytes()
CVE-2026-33020 7.1 HIGH libsixel: Integer Overflow in write_png_to_file() leads to Heap-based Buffer Overflow
CVE-2026-33018 7.0 HIGH libsixel: Use-After-Free in load_gif()

IV. Related Vulnerabilities

Same product: libsixel
Same vendor: saitoha
Same weakness: CWE-125

V. Comments for CVE-2026-33019

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