There is a heap-based buffer over-read in the Exiv2::Internal::PngChunk::keyTXTChunk function of pngchunk_int.cpp in Exiv2 0.26. A crafted PNG file will lead to a remote denial of service attack.
"https://github.com/pypa/advisory-database/blob/main/vulns/exiv2/PYSEC-2017-140.yaml"