CVE-2026-104861 probe-image-size: Quadratic-time Denial of Service in the SVG Parser
An attacker can cause a denial of service by sending crafted SVG data that triggers quadratic-time regex scanning, blocking the Node.js event loop.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-104861?
CVE-2026-104861 is a high-severity denial of service vulnerability in nodeca probe-image-size, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
probe-image-size gets image dimensions without downloading the entire file. Prior to 7.4.0, lib/parse_sync/svg.js and lib/parse_stream/svg.js use the searching regular expression /<[-_.:a-zA-Z0-9][^>]*>/, which repeatedly scans to the end of input when attacker-controlled data contains many less-than characters without a closing greater-than character. The synchronous parser converts and scans the full supplied buffer without an input cap, while the streaming parser reparses the complete accumulated SVG prefix for every received chunk. The probe.sync(), probe(stream), and probe(url) entry points can therefore block the Node.js event loop at full CPU, and attacker-controlled chunking can amplify the streaming cost. This issue is fixed in version 7.4.0.
Which versions are affected by CVE-2026-104861?
2 open source packages ship an affected version, including probe-image-size.
| Package | Affected | Fixed in |
|---|---|---|
probe-image-size npm | All versions | 7.4.0 |
probe-image-size npm | All versions | 7.4.0 |
How do I fix CVE-2026-104861?
Upgrade probe-image-size to 7.4.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-104861 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-104861 exists.
Sources
Also known as CLSA-2026-1791028047, CLSA-2026-1792489910, GHSA-gjj5-9665-rwrc, MINI-wj6p-gj4m-pwxp, MINI-wmq9-crw2-6xvg.