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CVE-2026-44637— libsixel: integer overflow in parser

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-r1及之前版本存在输入验证错误漏洞，该漏洞源于SIXEL解析器图像缓冲区加倍循环中的有符号整数溢出，可能导致越界堆写入。

CVSS 7.1 · High EPSS 0.17% · P5

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 1

VendorProduct Version RangeStatus
saitoha libsixel >= 0.11.0, < 1.8.7-r2 affected
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I. Basic Information for CVE-2026-44637

Vulnerability Information
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Vulnerability Title
libsixel: integer overflow in parser
Source: CVE Program / CVE List V5
Vulnerability Description
libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. context->pos_x grows by repeat_count on every sixel character with no upper bound check. Once pos_x approaches INT_MAX, the expression "pos_x + repeat_count" used to size the image buffer overflows signed int. Depending on how the overflow wraps, the resize check that should reject oversized buffers can be bypassed, after which a subsequent write computes a large attacker-influenced offset into image->data and writes past the allocation. Reachable from any caller that decodes attacker-supplied SIXEL data, including img2sixel. This vulnerability is fixed in 1.8.7-r2.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
整数溢出或超界折返
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-r1及之前版本存在输入验证错误漏洞，该漏洞源于SIXEL解析器图像缓冲区加倍循环中的有符号整数溢出，可能导致越界堆写入。
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 >= 0.11.0, < 1.8.7-r2 -

II. Public POCs for CVE-2026-44637

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III. Intelligence Information for CVE-2026-44637

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Vendor Advisories for CVE-2026-44637 (1)

Same Patch Batch · saitoha · 2026-05-14 · 3 CVEs total

CVE-2026-44636 7.4 HIGH libsixel: integer overflow in encoder
CVE-2026-44638 2.5 LOW libsixel: NULL pointer dereference

IV. Related Vulnerabilities

Same product: libsixel
Same vendor: saitoha
Same weakness: CWE-190

V. Comments for CVE-2026-44637

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