# CVE-2026-88052: Tesseract heap out-of-bounds write in UNICHARSET loading

Source: https://junglewise.ai/threats/cve-2026-88052-tesseract-heap-out-of-bounds-write-in-unicharset-loading  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-10. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-88052 · Severity: high · CVSS 7.8 · Published 2026-09-10

Tesseract is an open-source optical character recognition (OCR) engine used to extract text from images and documents. A vulnerability in how it loads character set definitions allows an attacker to craft a malformed file that triggers memory corruption, potentially crashing the application or enabling further exploitation during document processing.

Technologies: [Tesseract OCR Tesseract](https://junglewise.ai/threats/technologies/tesseract). Vendors: [Tesseract OCR](https://junglewise.ai/threats/vendors/tesseract-ocr).

## Quick answers

**Is CVE-2026-88052 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-88052 being exploited in the wild.

**How severe is CVE-2026-88052?** High severity, with a CVSS score of 7.8, published 10 September 2026.

**Which products and versions are affected?** Tesseract OCR Tesseract 5.5.3 and earlier.

**Is there a fix for CVE-2026-88052?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-88052 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-88052?** Check whether you run Tesseract OCR Tesseract at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a heap out-of-bounds write (CWE-787, CWE-129) in UNICHARSET::load_via_fgets (src/ccutil/unicharset.cpp). The function trusts a declared unichar count from the file as a loop bound and uses the loop index as an unchecked array index into the unichars vector. Because unichar_insert is a no-op for duplicate, empty, or already-encodable character representations, the vector size desynchronizes from the loop counter; subsequent set_* calls and property assignments write past the vector's end. The vulnerability is reachable at engine initialization via both LSTM (TESSDATA_LSTM_UNICHARSET) and legacy engine paths, and can be triggered by crafting a unicharset file with a duplicate character entry. No patched release is available as of the advisory date.

## Affected products

- tesseract-ocr Tesseract 5.5.3 and earlier

## Timeline

- 2026-08-25: disclosed: GitHub Security Advisory GHSA-2hm8-q5c7-c373 published
- 2026-09-10: advisory: NVD entry published for CVE-2026-88052

## References

- [https://github.com/tesseract-ocr/tesseract/commit/2d04d640db2e8c7e3bab2369d599343b5a8b8443](https://github.com/tesseract-ocr/tesseract/commit/2d04d640db2e8c7e3bab2369d599343b5a8b8443)
- [https://github.com/tesseract-ocr/tesseract/security/advisories/GHSA-2hm8-q5c7-c373](https://github.com/tesseract-ocr/tesseract/security/advisories/GHSA-2hm8-q5c7-c373)

## Related threats

- [Tesseract unsafe pointer deserialization in adaptive templates](https://junglewise.ai/threats/cve-2026-119341-tesseract-is-an-open-source-ocr-engine-prior-to-5-5-4)
- [Tesseract matrix deserialization integer overflow denial of service](https://junglewise.ai/threats/cve-2026-119340-tesseract-is-an-open-source-ocr-engine-prior-to-5-5-4-generic-2d)
- [Tesseract empty network stack denial of service in model deserialization](https://junglewise.ai/threats/cve-2026-88054-tesseract-empty-network-stack-denial-of-service-in-model)
- [Tesseract OCR heap out-of-bounds write in inttemp deserialization](https://junglewise.ai/threats/cve-2026-88053-tesseract-ocr-heap-out-of-bounds-write-in-inttemp-deserialization)
- [Tesseract heap out-of-bounds write in GenericVector::read](https://junglewise.ai/threats/cve-2026-88051-tesseract-heap-out-of-bounds-write-in-genericvector-read)