---
id: CVE-2026-12478
title: >-
  The fix for CVE-2026-0716 (commit 6ff7ef0, libsoup 3.6.6) placed the integer
  overflow guard inside the if (masked) block, leaving unmasked server-to-client
  frames unprotected
summary: >-
  The fix for CVE-2026-0716 (commit 6ff7ef0, libsoup 3.6.6) placed the integer
  overflow guard inside the if (masked) block, leaving unmasked server-to-client
  frames unprotected. A malicious WebSocket server can send a crafted unmasked
  fram…
severity: medium
cvss: 4.8
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L'
cwe:
  - CWE-125
vendor: Red Hat
product: libsoup3
affected:
  - libsoup3
  - libsoup
  - libsoup
  - libsoup
  - libsoup
published: '2026-07-14'
updated: '2026-09-16'
sourceUpdated: '2026-09-16T09:17:03.437'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-12478'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-12478'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2489655'
    label: secalert@redhat.com
  - url: 'https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/518'
    label: secalert@redhat.com
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12478.json
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-12478'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-12478'
tags:
  - nvd
  - exploit-available
  - cve.org
  - csaf
  - vex
  - red-hat
epss: 0.00388
epssPercentile: 0.3014
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/Popy21/security-research'
  checkedAt: '2026-09-26T09:05:37.577Z'
exploitAvailable: true
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-07-15T14:42:08.156943Z'
ingestedAt: '2026-09-15T20:44:02.379Z'
---

## Overview

The fix for CVE-2026-0716 (commit 6ff7ef0, libsoup 3.6.6) placed the integer overflow guard inside the if (masked) block, leaving unmasked server-to-client frames unprotected. A malicious WebSocket server can send a crafted unmasked frame with a payload length near UINT64_MAX to trigger an OOB read in a libsoup-based client when max_incoming_payload_size is set to 0.

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9 · updated 2026-09-16 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-12478.json)