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Fencer Vulns
medium 4.8

CVE-2026-12549 json

Libsoup: incomplete fix for cve-2026-2443: range suffix overflow in libsoup soupserver

published 2026-06-22 4 mo ago modified 2026-11-05 3 d ago also EUVD-2026-38279

cvss
4.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 29%
public exploits
0
none known

Summary

The fix for CVE-2026-2443 was regressed by a subsequent rework commit that replaced specific overflow checks with a general signed comparison. When a client sends a Range request with a suffix length exceeding the content size, the resulting negative start value is not properly clamped, leading to malformed HTTP 206 responses and log flooding.

Patch / fix

  • libsoup3 Debian 14 3.8.0-1

debian advisories DEBIAN-CVE-2026-12549

  • libsoup3 Ubuntu 24.04 LTS 3.4.4-5ubuntu0.9
  • libsoup3 Ubuntu 26.10 3.6.6-1ubuntu3
  • libsoup3 Ubuntu 26.04 LTS 3.6.6-1ubuntu0.1
  • libsoup2.4 Ubuntu 22.04 LTS 2.74.2-3ubuntu0.9
  • libsoup2.4 Ubuntu 24.04 LTS 2.74.3-6ubuntu1.9
  • libsoup3 Ubuntu Pro 22.04 LTS 3.0.7-0ubuntu1+esm9
  • libsoup2.4 Ubuntu Pro 16.04 LTS 2.52.2-1ubuntu0.3+esm8
  • libsoup2.4 Ubuntu Pro 18.04 LTS 2.62.1-1ubuntu0.4+esm9

ubuntu advisories UBUNTU-CVE-2026-12549

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-12549 updated cvss 4.8

libsoup: Incomplete fix for CVE-2026-2443: Range suffix overflow in libsoup SoupServer

  • Red Hat Enterprise Linux 6 libsoup Red Hat Enterprise Linux 7 libsoup
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 libsoup Red Hat Enterprise Linux 9 libsoup Red Hat Enterprise Linux 10 libsoup3
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 29% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • gitlab.gnome.org https://gitlab.gnome.org/GNOME/libsoup/-/work_items/516 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 4.8 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L

Affected products

  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9

Classification

Weakness
  • CWE-805 Buffer Access with Incorrect Length Value

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.