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VulnerabilityPublished Updated

CVE-2026-66338: Libsoup2.4 · A flaw was found in libsoup

Affects libsoup2.4Source GCVE Database

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Mentioned vulnerabilities

Authoritative record:CVE-2026-66338· Medium 5.4

Not known to be exploited · CVSS 5.4 Medium.

Data as of 3 Nov 2026, 23:19 UTC

CVSS 3.1 base score
5.4Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 3 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10libsoup2.4pkg:deb/ubuntu/libsoup2.4?arch=source&distro=stonkingOther threatsAffected
  • =2.74.3-10.1ubuntu5
Fixed in–
Ubuntu 26.10libsoup3pkg:deb/ubuntu/libsoup3?arch=source&distro=stonkingOther threatsAffected
  • =3.6.6-1
  • =3.6.6-1ubuntu3
  • =3.6.6-1ubuntu3.1
Fixed in–
Ubuntu 26.04 LTSlibsoup3pkg:deb/ubuntu/libsoup3?arch=source&distro=resoluteOther threatsAffected
  • 3.6.5-4 – 3.6.6-1ubuntu0.2
8 affected builds
Fixed in–
Ubuntu Pro 26.04 LTSlibsoup2.4pkg:deb/ubuntu/libsoup2.4?arch=source&distro=esm-apps/resoluteOther threatsAffected
  • 2.74.3-10.1ubuntu4 – 2.74.3-10.1ubuntu5+esm4
6 affected builds
Fixed in–
Ubuntu 24.04 LTSlibsoup2.4pkg:deb/ubuntu/libsoup2.4?arch=source&distro=nobleOther threatsAffected
  • 2.74.3-1 – 2.74.3-6ubuntu1.10
16 affected builds
Fixed in–
Ubuntu 24.04 LTSlibsoup3pkg:deb/ubuntu/libsoup3?arch=source&distro=nobleOther threatsAffected
  • 3.4.2-4 – 3.4.4-5ubuntu0.10
17 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

No explicit patch links are provided in the advisory. Since libsoup servers are rarely deployed in internet-facing roles behind strict proxies, the practical risk is limited. Users should monitor official vendor advisories for patches or updates addressing this issue.

Description

A vulnerability in libsoup's chunked transfer encoding parser allows permissive parsing of chunk sizes that violate RFC 9112. This flaw can be exploited to smuggle HTTP requests when libsoup is deployed behind a strict frontend proxy. The practical impact is limited due to the rare deployment of libsoup servers in internet-facing roles behind reverse proxies.

References

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