vulnerability / NVI-00018482 / Revision 1
Starlette: request.form() limits silently ignored for application/x-www-form-urlencoded enable DoS
GitHub lists this reviewed advisory for starlette. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
7.5 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
starlette
source listed>= 0.4.1, < 1.3.1
### Summary `request.form()` accepts `max_fields` and `max_part_size` to bound resource consumption while parsing form data. These limits are enforced for `multipart/form-data`, but silently ignored for `application/x-www-form-urlencoded`. An unauthenticated attacker can therefore send a urlencoded body with an arbitrarily large number of fields or an arbitrarily large field, even when the application configured limits it believed would apply. ### Details `request.form()` dispatches to a different parser depending on the `Content-Type`. For `multipart/form-data` the `max_files`, `max_fields`, and `max_part_size` limits are forwarded to the parser, but for `application/x-www-form-urlencoded` the parser is constructed without them. It has no `max_fields` or `max_part_size` parameter to receive them, and it appends every field with no count check and accumulates each field's name and value with no size check. The configured limits are therefore both unreachable and unenforced for url-encoded bodies. Because the url-encoded parser does its work synchronously between stream reads, the two attack shapes have different effects: - **Field count** drives CPU and event-loop blocking. A bo
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-82w8-qh3p-5jfq ↗
GitHub Advisory Database · vendor advisory
Observed . GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.
Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.