---
id: CVE-2026-66337
title: >-
  Libsoup: libsoup: heap buffer over-read via integer underflow in
  soup_filter_input_stream_read_until()
summary: >-
  A flaw was found in libsoup. An unsigned integer underflow in the
  soup_filter_input_stream_read_until() function causes a heap buffer over-read
  when parsing multipart HTTP responses. A malicious HTTP server can exploit
  this by sending a …
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L'
cvssSource: cna
cwe:
  - CWE-125
vendor: Red Hat
product: libsoup3
affected:
  - libsoup3 (all versions)
  - libsoup (all versions)
  - libsoup (all versions)
  - libsoup (all versions)
  - libsoup (all versions)
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-07-27T16:01:07.951976Z'
published: '2026-07-24'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T22:13:09.637Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-66337'
references:
  - url: 'https://access.redhat.com/security/cve/CVE-2026-66337'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2506949'
    label: RHBZ#2506949
tags:
  - cve.org
epss: 0.00246
epssPercentile: 0.15968
ingestedAt: '2026-11-05T23:41:31.953Z'
---

## Overview

A flaw was found in libsoup. An unsigned integer underflow in the soup_filter_input_stream_read_until() function causes a heap buffer over-read when parsing multipart HTTP responses. A malicious HTTP server can exploit this by sending a crafted multipart response, potentially causing the client application to crash or disclose sensitive heap memory.

## Affected

- `libsoup3 (all versions)`
- `libsoup (all versions)`
- `libsoup (all versions)`
- `libsoup (all versions)`
- `libsoup (all versions)`

## Remediation

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