---
id: CVE-2026-103635
title: >-
  Out-of-bounds read in the compact Theta sketch deserialization of Apache
  DataSketches C++ (repo: datasketches-cpp).


  compact_theta_sketch::deserialize() and wrapped_compact_theta_sketch::wrap()
  read header fields before checking that the…
summary: >-
  Out-of-bounds read in the compact Theta sketch deserialization of Apache
  DataSketches C++ (repo: datasketches-cpp).


  compact_theta_sketch::deserialize() and wrapped_compact_theta_sketch::wrap()
  read header fields before checking that the…
severity: none
cwe:
  - CWE-125
  - CWE-190
published: '2026-10-10'
updated: '2026-10-10'
sourceUpdated: '2026-10-10T13:17:31.060'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-103635'
references:
  - url: 'https://github.com/apache/datasketches-cpp/releases/tag/5.3.0'
    label: security@apache.org
  - url: 'https://lists.apache.org/thread/15b86y9jstco39kzppjw7l5kvhjvwqvv'
    label: security@apache.org
  - url: 'http://www.openwall.com/lists/oss-security/2026/10/10/5'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
ingestedAt: '2026-10-10T11:31:21.932Z'
epss: 0.00198
epssPercentile: 0.08815
---

## Overview

Out-of-bounds read in the compact Theta sketch deserialization of Apache DataSketches C++ (repo: datasketches-cpp).

compact_theta_sketch::deserialize() and wrapped_compact_theta_sketch::wrap() read header fields before checking that the input was long enough. For the compressed format, the size check could be defeated by a 32-bit overflow, and two header fields that control decoding were not validated; this also affected deserialization from a stream. A crafted or truncated sketch could cause a read past the end of the input. In the compressed case the over-read can be large, and the bytes read can become part of the deserialized sketch. This can cause a crash (denial of service) and could expose adjacent memory contents.

This issue affects Apache DataSketches C++: from 3.1.0 before 5.3.0. Only applications that deserialize Theta sketches from untrusted sources are affected.

Users are recommended to upgrade to version 5.3.0, which fixes this issue.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.