An underflow read was found in pngcheckkeyword in pngwutil.c in libpng-1.2.54:

If the data of "key" is only ' ' (0x20), it will read a byte before the buffer in line 1288.

This issue impacts upstream versions 1.2.55, 1.0.65, 1.4.18, and 1.5.25 of libpng.

An attacker could possibly use this flaw to cause an out-of-bounds read by tricking an unsuspecting user into processing a specially crafted PNG image.

CVE assignment:

http://seclists.org/oss-sec/2015/q4/469

Upstream issue:

http://sourceforge.net/p/libpng/bugs/244/

Upstream patch:

http://sourceforge.net/p/libpng/code/ci/d9006f683c641793252d92254a75ae9b815b42ed/

Buffer overflow in libpng allows remote attackers to cause a denial of service

Last updated 18 August 2026

Memory leak in the pnghandletEXt function in pngrutil.c in libpng before 1.2.33 rc02 and 1.4.0 beta36 allows context-dependent attackers to cause a denial of service (memory exhaustion) via a crafted PNG file.

The PNG reference library (aka libpng) before 1.0.43, and 1.2.x before 1.2.35, as used in pngcrush and other applications, allows context-dependent attackers to cause a denial of service (application crash) or possibly execute arbitrary code via a crafted PNG file that triggers a free of an uninitialized pointer in (1) the pngreadpng function, (2) pCAL chunk handling, or (3) setup of 16-bit gamma tables.

From: Steve G <linux4ever>

In the pngformatbuffer function located in pngerror.c around line 133 is the following code:

if (message == NULL) buffer[iout] = 0; else { buffer[iout++] = ':'; buffer[iout++] = ' '; pngmemcpy(buffer+iout, message, 64); buffer[iout+63] = 0; } This code is called from the pngchunkerror & pngchunkwarning functions. An example of their use would be in pngutil.c around line 119. pngchunkerror(pngptr, "CRC error"); In the above code, the message being constructed is only 10 characters long. The pngmemcpy function will unconditionally access 54 bytes beyond the message.

This could cause a carefully crafted png image to cause a denial of service.

Possibly embargoed; marking as embargoed until communicated otherwise.

The pngcheckkeyword function in pngwutil.c in libpng before 1.0.42, and 1.2.x before 1.2.34, might allow context-dependent attackers to set the value of an arbitrary memory location to zero via vectors involving creation of crafted PNG files with keywords, related to an implicit cast of the '\0' character constant to a NULL pointer. NOTE: some sources incorrectly report this as a double free vulnerability.

The pngpushreadzTXt function in pngpread.c in libpng 1.0.x before 1.0.58, 1.2.x before 1.2.48, 1.4.x before 1.4.10, and 1.5.x before 1.5.10 allows remote attackers to cause a denial of service (out-of-bounds read) via a large availin field value in a PNG image.

libpng before 1.2.37 does not properly parse 1-bit interlaced images with width values that are not divisible by 8, which causes libpng to include uninitialized bits in certain rows of a PNG file and might allow remote attackers to read portions of sensitive memory via "out-of-bounds pixels" in the file.

The pngdecompresschunk function in pngrutil.c in libpng 1.0.x before 1.0.53, 1.2.x before 1.2.43, and 1.4.x before 1.4.1 does not properly handle compressed ancillary-chunk data that has a disproportionately large uncompressed representation, which allows remote attackers to cause a denial of service (memory and CPU consumption, and application hang) via a crafted PNG file, as demonstrated by use of the deflate compression method on data composed of many occurrences of the same character, related to a "decompression bomb" attack.

Off-by-one error in ICC profile chunk handling in the pngsetiCCP function in pngset.c in libpng before 1.0.29 beta1 and 1.2.x before 1.2.21 beta1 allows remote attackers to cause a denial of service (crash) via a crafted PNG image that prevents a name field from being NULL terminated.

pngrtran.c in libpng before 1.0.29 and 1.2.x before 1.2.21 use (1) logical instead of bitwise operations and (2) incorrect comparisons, which might allow remote attackers to cause a denial of service (crash) via a crafted PNG image.