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CVE-2026-44638— libsixel: NULL pointer dereference

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及之前版本存在代码问题漏洞，该漏洞源于分配调用后错误的NULL检查，可能导致空指针取消引用，造成拒绝服务。

CVSS 2.5 · Low EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
saitoha libsixel >= 1.0.0, < 1.8.7-r2 affected
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I. Basic Information for CVE-2026-44638

Vulnerability Information
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Vulnerability Title
libsixel: NULL pointer dereference
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 wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
空指针解引用
Source: CVE Program / CVE List V5
Vulnerability Title
libsixel 代码问题漏洞
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及之前版本存在代码问题漏洞，该漏洞源于分配调用后错误的NULL检查，可能导致空指针取消引用，造成拒绝服务。
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 >= 1.0.0, < 1.8.7-r2 -

II. Public POCs for CVE-2026-44638

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III. Intelligence Information for CVE-2026-44638

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Vendor Advisories for CVE-2026-44638 (1)

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

CVE-2026-44636 7.4 HIGH libsixel: integer overflow in encoder
CVE-2026-44637 7.1 HIGH libsixel: integer overflow in parser

IV. Related Vulnerabilities

Same product: libsixel
Same vendor: saitoha
Same weakness: CWE-476

V. Comments for CVE-2026-44638

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