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CVE-2026-12478VulnerabilityPublished Updated

Libsoup3: The fix for CVE-2026-0716 (commit 6ff7ef0, libsoup 3.6.6) placed the integer overflow guard inside the if

Affects libsoup3Source GCVE Database

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Mentioned vulnerabilities

Authoritative record:CVE-2026-12478· Medium 4.8

Not known to be exploited · CVSS 4.8 Medium.

Data as of 3 Nov 2026, 23:14 UTC

CVSS 3.1 base score
4.8Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 14 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 26.10libsoup3pkg: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 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–
Ubuntu Pro 22.04 LTSlibsoup3pkg:deb/ubuntu/libsoup3?arch=source&distro=esm-apps/jammyOther threatsAffected
  • 3.0.4-2 – 3.0.7-0ubuntu1+esm10
14 affected builds
Fixed in–

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Description

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.

References

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