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CVE-2026-25646— LIBPNG has a heap buffer overflow in png_set_quantize

Quick assessment

Affected
pnggroup libpng
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

libpng是The PNG Development Group开源的一个可对PNG图形文件实现创建、读写等操作的PNG参考库。 libpng 1.6.55之前版本存在安全漏洞，该漏洞源于png_set_quantize函数存在越界读取，可能导致无限循环和堆缓冲区读取越界。

CVSS 8.3 · High EPSS 1.09% · P66

Affected Version Matrix 1

VendorProduct Version RangeStatus
pnggroup libpng < 1.6.55 affected
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I. Basic Information for CVE-2026-25646

Vulnerability Information
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Vulnerability Title
LIBPNG has a heap buffer overflow in png_set_quantize
Source: CVE Program / CVE List V5
Vulnerability Description
LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. Prior to 1.6.55, an out-of-bounds read vulnerability exists in the png_set_quantize() API function. When the function is called with no histogram and the number of colors in the palette is more than twice the maximum supported by the user's display, certain palettes will cause the function to enter into an infinite loop that reads past the end of an internal heap-allocated buffer. The images that trigger this vulnerability are valid per the PNG specification. This vulnerability is fixed in 1.6.55.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
堆缓冲区溢出
Source: CVE Program / CVE List V5
Vulnerability Title
libpng 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
libpng是The PNG Development Group开源的一个可对PNG图形文件实现创建、读写等操作的PNG参考库。 libpng 1.6.55之前版本存在安全漏洞，该漏洞源于png_set_quantize函数存在越界读取，可能导致无限循环和堆缓冲区读取越界。
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
pnggroup libpng < 1.6.55 -

II. Public POCs for CVE-2026-25646

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 12963 chars
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III. Intelligence Information for CVE-2026-25646

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IV. Related Vulnerabilities

Same product: libpng
Same vendor: pnggroup
Same weakness: CWE-122