---
id: CVE-2026-103501
title: >-
  Heap buffer overflow in the HLL sketch deserialization of Apache DataSketches
  C++ (repo: datasketches-cpp).


  When deserializing a sketch in LIST mode, from either a byte buffer or a
  stream, the coupon count was read from the input and us…
summary: >-
  Heap buffer overflow in the HLL sketch deserialization of Apache DataSketches
  C++ (repo: datasketches-cpp).


  When deserializing a sketch in LIST mode, from either a byte buffer or a
  stream, the coupon count was read from the input and us…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cwe:
  - CWE-122
  - CWE-1284
vendor: Apache Software Foundation
product: apache/datasketches-cpp
affected:
  - apache/datasketches-cpp >= 1.0.0-incubating <= 5.2.0
published: '2026-10-10'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T16:16:53.233'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-103501'
references:
  - url: 'https://github.com/apache/datasketches-cpp/releases/tag/5.3.0'
    label: security@apache.org
  - url: 'https://lists.apache.org/thread/n2oc2j841dzsv4239jjp08of66bo79c5'
    label: security@apache.org
  - url: 'http://www.openwall.com/lists/oss-security/2026/10/10/2'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - cve.org
epss: 0.00555
epssPercentile: 0.46128
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T15:21:43.590609Z'
ingestedAt: '2026-10-10T11:31:21.931Z'
---

## Overview

Heap buffer overflow in the HLL sketch deserialization of Apache DataSketches C++ (repo: datasketches-cpp).

When deserializing a sketch in LIST mode, from either a byte buffer or a stream, the coupon count was read from the input and used as the number of entries to copy into a fixed buffer of 8 entries, without checking it against the buffer's capacity. A crafted sketch could cause a write of up to 988 bytes past the end of this internal heap buffer. This can corrupt heap memory, causing a crash and potentially enabling further exploitation.

This issue affects Apache DataSketches C++: from 1.0.0-incubating before 5.3.0. Only applications that deserialize HLL 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.