CVE-2025-4969

What it actually does

The flaw prevents correct verification of multipart HTTP message termination in libsoup, enabling a remote attacker to supply a crafted body that triggers an out-of-bounds read beyond allocated memory buffers in any server process consuming the library.

Why it matters to the business

Organizations running affected Ubuntu server packages face potential service crashes or limited information disclosure from web or HTTP-handling workloads; the large number of dependent packages across LTS releases increases patch management scope, though low exploit maturity reduces immediate operational urgency.

How an attack unfolds

An attacker sends a specially crafted multipart HTTP request lacking proper termination markers to a libsoup-based server; the library fails to bound-check the message, resulting in an out-of-bounds memory read that may leak data or cause a crash.

How to fix it

Upgrade each affected package to the listed fixed version for the corresponding Ubuntu release (examples: linux 3.11.0-12.19 on 14.04 LTS, linux-aws 4.4.0-1002.2 on 14.04 LTS, linux 4.4.0-2.16 on 16.04 LTS, linux 4.13.0-16.19 on 18.04 LTS, linux 5.4.0-9.12 on 20.04 LTS, and equivalent updates for all listed variants). Restart affected services after upgrade and verify the new package version is active.

How to confirm the fix worked

Confirm the installed package version matches or exceeds the fixed release for each distribution; re-test multipart HTTP handling with both valid and boundary-case payloads to ensure no out-of-bounds access occurs; monitor process stability under load.

Typical attack path

1. Identify a publicly reachable HTTP endpoint served by an application linked against vulnerable libsoup
2. Craft and transmit a multipart request body with malformed or missing termination boundaries
3. Trigger the out-of-bounds read during message parsing
4. Observe either a process crash or attempt to extract leaked memory contents for further exploitation

How to detect it

Review web server and application logs for unusually large or malformed multipart POST/PUT requests; correlate with process crashes or segmentation faults in services linked to libsoup; examine memory dumps or core files for evidence of out-of-bounds access if crashes occur.

What your security team should do

• Prioritize patching of internet-facing systems within standard change windows given the low EPSS and absence from KEV
• Inventory all servers using libsoup or the listed kernel packages and schedule staged rollouts
• Apply the exact fixed versions provided for each Ubuntu release
• Update detection rules to watch for anomalous multipart request sizes or termination patterns