Tesseract is an open source OCR engine. In version 5.5.3 and earlier, Plumbing::DeSerialize in src/lstm/plumbing.cpp rejects excessively large network stacks but accepts a zero-length stack for NTSERIES, NTPARALLEL, or NTREVERSED layers in a crafted .traineddata model. During LSTMRecognizer initialization in src/lstm/lstmrecognizer.cpp, CacheXScaleFactor(XScaleFactor()) reaches Series::CacheXScaleFactor in src/lstm/series.cpp, which dereferences stack[0] on the empty vector and invokes a virtual method through an invalid Network pointer. This causes a deterministic crash and denial of service at model load. No fixed release is available as of this review.

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. In version 5.5.3 and earlier, the callback form of GenericVector::read in src/ccutil/genericvector.h reads the independent int32 fields reserved and sizeused from a .traineddata model without a cap or an invariant check. reserve(reserved) allocates the backing array, but the callback loop writes sizeused elements. A crafted TESSDATAINTTEMP component with versionid 4 or later can therefore set reserved to a small value and sizeused to a large value when fontinfotable.read(fp, readinfo) is called from src/classify/intproto.cpp, causing a heap out-of-bounds write of FontInfo structures, 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, FullyConnected::DeSerialize in src/lstm/fullyconnected.cpp does not validate the deserialized layer scalars ni and no against the weight-matrix dimensions. During FullyConnected::Forward, MatrixDotVector in src/lstm/weightmatrix.cpp writes w.dim1() results into templine, which is sized from no, and reads w.dim2() minus one inputs from currinput, which is sized from ni. A crafted .traineddata NTSOFTMAX layer can therefore use inconsistent dimensions to cause a heap out-of-bounds write and read on the default LSTM engine, resulting in heap corruption, a crash, information disclosure, 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 LSTM model component loaded through Tesseract's deserializer can cause an unchecked signed integer multiplication in Convolve::DeSerialize in src/lstm/convolve.cpp to wrap the convolution output-channel count, undersizing the forward-pass output buffer while writes use the unwrapped element count and causing a heap out-of-bounds write during OCR recognition. This issue is fixed in version 5.5.3.

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.