Tesseract is an open source OCR engine. In version 5.5.3 and earlier, Classify::ReadIntTemplates in src/classify/intproto.cpp reads NumClassPruners, NumClasses, and NumProtoSets from the TESSDATAINTTEMP component of a crafted .traineddata file and uses those values as loop bounds without validating them against MAXNUMCLASSPRUNERS, MAXNUMCLASSES, and MAXNUMPROTOSETS. The loops store heap pointers into fixed-capacity ClassPruners and ProtoSets arrays in INTTEMPLATESSTRUCT and INTCLASSSTRUCT, so an oversized count causes heap out-of-bounds pointer writes during legacy-classifier initialization before OCR begins, resulting in heap corruption, a crash, or potentially controlled corruption. No fixed release is available as of this review.

Tesseract is an open source OCR engine. In version 5.5.3 and earlier, UNICHARSET::loadviafgets in src/ccutil/unicharset.cpp trusts the declared unichar count as a loop bound and uses id as an unchecked index into the unichars vector. unicharinsertbackwardscompatible can leave the vector unchanged for an empty, duplicate, or already-encodable representation, causing id to become larger than unichars.size(). Subsequent set calls and the write to unichars[id].properties.enabled then write UNICHARPROPERTIES beyond the vector during initialization in both the default LSTM and legacy engines, causing heap corruption, a crash, or potentially controlled corruption. No fixed release is available as of this review.

Tesseract is an open source OCR engine. Prior to 5.5.3, a crafted .traineddata model loaded through TessBaseAPI::Init can cause SquishedDawg::readsquisheddawg in src/dict/dawg.cpp to accept an unterminated forward-edge run, after which SquishedDawg::Load calls numforwardedges(0) and lastedge in src/dict/dawg.h reads beyond edges, causing a heap out-of-bounds read and process crash before image processing. This issue is fixed in version 5.5.3.