# CVE-2026-12478: Libsoup: incomplete fix for cve-2026-0716: out-of-bounds read in libsoup websocket frame processing (unmasked path)

> A malicious WebSocket server can trigger an out-of-bounds read in libsoup clients via crafted unmasked frames when payload size limits are disabled.

- **Severity:** Medium 4.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Jul 2026
- **Updated:** 16 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-12478, GHSA-6jpc-6452-qwq2, OESA-2026-3380, OESA-2026-3381, OESA-2026-3382, OESA-2026-3383, OESA-2026-3441, OESA-2026-3553, OESA-2026-3554, SUSE-SU-2026:23800-1, UBUNTU-CVE-2026-12478, openSUSE-SU-2026:11316-1, openSUSE-SU-2026:21871-1

## What is CVE-2026-12478?

CVE-2026-12478 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-12478?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libsoup` | SUSE:Linux Micro 6.2 | All versions | 3.6.6-160000.3.1 |
| `libsoup` | openSUSE:Leap 16.0 | All versions | 3.6.6-160000.3.1 |
| `libsoup` | openSUSE:Tumbleweed | All versions | 3.6.6-7.1 |

## How do I fix CVE-2026-12478?

Apply the vendor's patch.

## Is CVE-2026-12478 being exploited?

There is no known exploitation of CVE-2026-12478 in the wild and no public exploit code.

Public exploit code:

- Vulnerability research write-ups — CVE-2026-12478 (libsoup), Apple WebKit, Google VRP (github_poc): https://github.com/Popy21/security-research

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12478 and fix it if it is affected.

What it is: CVE-2026-12478 is a medium-severity vulnerability in Red Hat Enterprise Linux 10, published on 14 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-12478 in the wild and no public exploit code.

Affected product: Red Hat Enterprise Linux 10. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-12478/ (Markdown: https://insights.sbomify.com/CVE-2026-12478/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12478
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12478
- OSV: https://osv.dev/vulnerability/CVE-2026-12478

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-12478/
Summaries are generated and may contain mistakes; the official description above is the record.