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.
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Potential Mitigations
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html
References
- https://github.com/nodeca/probe-image-size/commit/60cc96ac0b671e79e328213d0a8e831312b09e84
- https://github.com/nodeca/probe-image-size/commit/9b74656d6f973cc59ea2ab1375c0d88390a402ad
- https://github.com/nodeca/probe-image-size/commit/c032aefabdecf5cb50548ab9ba175db56353078f
- https://github.com/nodeca/probe-image-size/releases/tag/7.4.0
- https://github.com/nodeca/probe-image-size/security/advisories/GHSA-gjj5-9665-rwrc
- https://github.com/nodeca/probe-image-size/security/advisories/GHSA-gjj5-9665-rwrc