CVE-2026-88047 in Tesseract
Summary
by MITRE • 09/10/2026
Tesseract is an open source OCR engine. In version 5.5.3 and earlier, Classify::ReadNormProtos in src/classify/normmatch.cpp parses the NORMPROTO component of a .traineddata file and uses std::istream::operator>>(char*) to extract a whitespace-delimited token into a fixed 61-byte stack buffer without setting a stream width. The 100-byte line buffer can carry a token of up to 99 characters, so a token longer than 60 characters writes up to 39 attacker-controlled bytes past the buffer during TessBaseAPI::Init of the legacy engine, causing stack corruption, denial of service, and potentially control-flow hijacking on affected standard-library implementations. Builds using Apple's libc++ C++20 bounded array overload are incidentally protected, while typical libstdc++ builds remain affected. No fixed release is available as of this review.
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Analysis
by VulDB Data Team • 09/10/2026
The vulnerability identified in Tesseract versions 5.5.3 and earlier represents a critical stack-based buffer overflow within the legacy OCR engine's initialization process. Specifically, the flaw resides in the Classify::ReadNormProtos function located in src/classify/normmatch.cpp, which is responsible for parsing the NORMPROTO component of .traineddata files. During this parsing operation, the code utilizes std::istream::operator>>(char*) to extract whitespace-delimited tokens from an input stream and writes them into a fixed 61-byte stack buffer. The implementation fails to set a stream width or otherwise constrain the extraction length, allowing any token exceeding sixty characters to overflow the allocated memory space. This specific coding error enables an attacker who can supply a maliciously crafted .traineddata file to write up to thirty-nine bytes of controlled data beyond the bounds of the stack buffer during the TessBaseAPI::Init phase.
The operational impact of this vulnerability is severe, primarily manifesting as immediate denial of service through application crash due to stack corruption. However, the security implications extend far beyond simple availability loss. On affected standard-library implementations, particularly those using libstdc++, the ability to overwrite adjacent memory on the stack creates a pathway for control-flow hijacking. An attacker could potentially manipulate return addresses or function pointers stored in close proximity to the buffer, leading to arbitrary code execution with the privileges of the process running Tesseract. It is important to note that builds utilizing Apple's libc++ C++20 bounded array overload are incidentally protected against this specific overflow mechanism due to stricter bounds checking inherent in their implementation, but the majority of deployments relying on standard libstdc++ remain fully vulnerable and at risk of remote code execution if processing untrusted training data.
From a classification perspective, this vulnerability aligns with CWE-121, which defines stack-based buffer overflow as a condition where an application writes data past the end or before the beginning of a stack-allocated buffer. The attack vector leverages CWE-787, specifically involving out-of-bounds write operations triggered by improper input validation during file parsing. In terms of adversarial tactics, this flaw facilitates initial access and potential privilege escalation through exploitation techniques categorized under ATT&CK T1203, which covers the execution of exploits or programs derived from vulnerabilities in software components. The lack of a fixed release as of the review period underscores the critical need for immediate defensive measures by organizations relying on these versions of Tesseract.
Mitigation strategies must focus on isolating the processing environment and validating input integrity before it reaches the vulnerable parsing logic. Since no official patch is currently available, administrators should restrict the use of legacy engine modes unless absolutely necessary, as modern alternatives may not be susceptible to this specific stack corruption vector. Implementing strict file type validation and ensuring that .traineddata files originate only from trusted sources can significantly reduce the attack surface. Additionally, deploying runtime protection mechanisms such as Stack Canaries or Address Space Layout Randomization can help detect or prevent exploitation attempts by mitigating the impact of memory corruption events. Organizations should also consider compiling Tesseract with security-hardened standard libraries if feasible, although this is not a universal solution given platform dependencies. Continuous monitoring for anomalous behavior during OCR initialization processes and updating to patched versions as soon as they are released remain essential components of a robust defense-in-depth strategy against this vulnerability.