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libsoup CVE-2026-12478

| EUVDEUVD-2026-43651 MEDIUM
Out-of-bounds Read (CWE-125)
2026-07-14 redhat GHSA-6jpc-6452-qwq2
4.8
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
4.8 MEDIUM
AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
vuln.today AI
4.8 MEDIUM

Network vector (attacker is the server); AC:H for dual precondition of max_incoming_payload_size=0 and attacker-controlled endpoint; no auth required from attacker's server role; OOB read yields only limited memory disclosure and potential crash.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L
4.0 AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative
Red Hat
4.8 MEDIUM
qualitative

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
Low

Lifecycle Timeline

2
Analysis Generated
Jul 14, 2026 - 10:17 vuln.today
CVE Published
Jul 14, 2026 - 09:26 cve.org
MEDIUM 4.8

DescriptionCVE.org

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.

AnalysisAI

Out-of-bounds read in libsoup 3.6.6 exposes WebSocket clients to memory disclosure and crashes when connecting to malicious servers. The incomplete fix for CVE-2026-0716 (commit 6ff7ef0) placed the integer overflow guard exclusively inside the masked-frame branch, leaving the unmasked server-to-client frame path entirely unprotected - allowing a crafted payload length near UINT64_MAX to bypass the guard entirely. No public exploit code or active exploitation (CISA KEV) has been identified, but the CVSS AC:H rating reflects the non-trivial preconditions: a specific client configuration and attacker-controlled server are both required.

Technical ContextAI

libsoup is GNOME's HTTP and WebSocket networking library, widely used by GTK/GNOME applications on Linux. The WebSocket protocol (RFC 6455) specifies that server-to-client frames must be unmasked, while client-to-server frames must be masked. The patch for CVE-2026-0716 introduced an integer overflow guard intended to prevent unsafe arithmetic on large payload-length fields, but the guard was conditionally scoped to the if (masked) branch. Because server frames are always unmasked, the guard is never reached for server-to-client traffic. CWE-125 (Out-of-bounds Read) describes the resulting condition: when max_incoming_payload_size is 0 (signaling no enforced limit), arithmetic on a near-UINT64_MAX payload length overflows, causing the parser to read beyond the allocated buffer. The CPE data ties this to Red Hat Enterprise Linux 10, and the upstream fix is tracked at GitLab MR 518 against the GNOME/libsoup repository.

RemediationAI

The upstream fix is available as libsoup GitLab merge request 518 at https://gitlab.gnome.org/GNOME/libsoup/-/merge_requests/518; however, a released tagged version incorporating this fix has not been independently confirmed from the available data - treat this as an upstream fix available via PR/commit rather than a shipped patched release. Distributions packaging libsoup should monitor for a point release that includes MR 518 and apply it promptly. The Red Hat advisory is tracked at https://access.redhat.com/security/cve/CVE-2026-12478 and Bugzilla entry 2489655. As a compensating control, applications consuming libsoup over WebSocket should avoid setting max_incoming_payload_size to 0 and instead configure an explicit upper bound, which prevents the overflow condition from being reachable regardless of server input. This control has the trade-off of rejecting legitimately large frames and may break applications designed to handle unbounded message sizes.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected

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CVE-2026-12478 vulnerability details – vuln.today

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