CVE-2026-12478: libsoup3 Out-of-bounds Read
Vulnerability summary
CVE-2026-12478 is a medium (CVSS 4.8) Out-of-bounds Read vulnerability in libsoup3. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14.3% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 5 · Related 5Timeline
- 14-07-2026PublishedVulnerability first disclosed.
- 16-09-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated4.8MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
- OSV · DebianEcosystem advisory · calculated4.8MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
- NVDNIST4.8MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
EPSS trend
Probability
0.24%
Chance of exploitation in the next 30 days
Percentile
14%
Versus all other CVEs
30-day change
-0.15 pp
From 0.39% on 21-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Opensuse2 products
- libsoup&distro=openSUSE Leap 16.0< 3.6.6-160000.3.1
- libsoup&distro=openSUSE Tumbleweed< 3.6.6-7.1
Debian1 product
- libsoup3All versions (No fix recorded) | < 3.8.0-1
Suse1 product
- libsoup&distro=SUSE Linux Micro 6.2< 3.6.6-160000.3.1
Ubuntu1 product
- libsoup3All versions (No fix recorded)
4 vendors · 5 products
