---
id: CVE-2026-102559
title: A flaw was found in libsoup
summary: >-
  A flaw was found in libsoup. When constructing a masked WebSocket client frame
  for a very large outgoing payload, size values passed to GByteArray allocation
  APIs could be truncated while the masking routine still used the full length,
  c…
severity: high
cvss: 8.6
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H'
cwe:
  - CWE-125
vendor: Red Hat
product: libsoup3
affected:
  - libsoup3 (all versions)
  - libsoup (all versions)
  - libsoup
  - libsoup (all versions)
  - libsoup (all versions)
published: '2026-09-29'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T17:17:09.633'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102559'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2026:83384'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2026:83618'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2026-102559'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2543285'
    label: secalert@redhat.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-102559.json
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-102559'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102559'
  - url: 'https://access.redhat.com/errata/RHSA-2026:84586'
    label: 'RHSA-2026:84586'
  - url: 'https://access.redhat.com/errata/RHSA-2026:92347'
    label: 'RHSA-2026:92347'
tags:
  - nvd
  - cve.org
  - csaf
  - vex
  - red-hat
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-30T19:42:40.159345Z'
epss: 0.00404
epssPercentile: 0.34438
ingestedAt: '2026-09-29T17:41:02.260Z'
patched:
  - enterprise_linux_appstream_v_10
  - enterprise_linux_appstream_v_8
  - enterprise_linux_appstream_v_9
  - enterprise_linux_baseos_v_8
  - enterprise_linux_codeready_linux_builder_v_10
---

## Overview

A flaw was found in libsoup. When constructing a masked WebSocket client frame for a very large outgoing payload, size values passed to GByteArray allocation APIs could be truncated while the masking routine still used the full length, causing a heap buffer overflow.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 · updated 2026-10-19 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-102559.json)
- **RHSA-2026:83618** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) · released 2026-10-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:83618)
- **RHSA-2026:84586** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux BaseOS (v. 8) · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84586)
- **RHSA-2026:83384** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9) · released 2026-10-15 · [advisory](https://access.redhat.com/errata/RHSA-2026:83384)