libpng up to 1.6.56 Chunk Setter API png_set_hIST use after free

Summaryinfo

A vulnerability marked as critical has been reported in libpng up to 1.6.56. This affects the function png_set_hIST of the component Chunk Setter API. The manipulation leads to use after free. This vulnerability is uniquely identified as CVE-2026-34757. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in libpng up to 1.6.56. It has been rated as critical. This issue affects the function png_set_hIST of the component Chunk Setter API. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. From 1.0.9 to before 1.6.57, passing a pointer obtained from png_get_PLTE, png_get_tRNS, or png_get_hIST back into the corresponding setter on the same png_struct/png_info pair causes the setter to read from freed memory and copy its contents into the replacement buffer. The setter frees the internal buffer before copying from the caller-supplied pointer, which now dangles. The freed region may contain stale data (producing silently corrupted chunk metadata) or data from subsequent heap allocations (leaking unrelated heap contents into the chunk struct). This vulnerability is fixed in 1.6.57.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-34757. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 305709 (Linux Distros Unpatched Vulnerability : CVE-2026-34757), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.6.57 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (305709), EUVD (EUVD-2026-20897) and CERT Bund (WID-SEC-2026-1023). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Amazon Linux 2
• SUSE Linux
• SUSE openSUSE
• Microsoft Azure Linux
• Open Source libpng

Productinfo

Type

• Image Processing Software

Name

• libpng

Version

• 1.6.0
• 1.6.1
• 1.6.2
• 1.6.3
• 1.6.4
• 1.6.5
• 1.6.6
• 1.6.7
• 1.6.8
• 1.6.9
• 1.6.10
• 1.6.11
• 1.6.12
• 1.6.13
• 1.6.14
• 1.6.15
• 1.6.16
• 1.6.17
• 1.6.18
• 1.6.19
• 1.6.20
• 1.6.21
• 1.6.22
• 1.6.23
• 1.6.24
• 1.6.25
• 1.6.26
• 1.6.27
• 1.6.28
• 1.6.29
• 1.6.30
• 1.6.31
• 1.6.32
• 1.6.33
• 1.6.34
• 1.6.35
• 1.6.36
• 1.6.37
• 1.6.38
• 1.6.39
• 1.6.40
• 1.6.41
• 1.6.42
• 1.6.43
• 1.6.44
• 1.6.45
• 1.6.46
• 1.6.47
• 1.6.48
• 1.6.49
• 1.6.50
• 1.6.51
• 1.6.52
• 1.6.53
• 1.6.54
• 1.6.55
• 1.6.56

License

• open-source

CPE 2.3info

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CPE 2.2info

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Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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