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8.7
Wisp Server Memory or Disk Overflow via Large Multipart Form Submissions
CVE-2026-32145
GHSA-8645-p2v4-73r2
GHSA-8645-p2v4-73r2
Summary
An attacker can cause a Wisp server to run out of memory or disk space by sending a large multipart form submission. This can happen if an attacker sends a big file or a lot of small files in a single HTTP request. To prevent this, update Wisp to version 2.2.2 or later.
What to do
- Update wisp to version 2.2.2.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| – | wisp | <= 2.2.2 | 2.2.2 |
Original title
wisp has Allocation of Resources Without Limits or Throttling
Original description
### Summary
A multipart form parsing bug allows any unauthenticated user to bypass configured request size limits and trigger a denial of service by exhausting server memory or disk.
### Details
The issue is in the multipart parsing logic, specifically in `multipart_body` and `multipart_headers`.
When parsing multipart data, the implementation distinguishes between:
- chunks where a boundary is found
- chunks where more data is required
In the normal case (boundary found), the parser correctly accounts for consumed bytes by calling `decrement_quota`.
However, in the `MoreRequiredForBody` branch, the parser appends incoming data to the output but recurses without decrementing the quota. This means that any chunk that does not contain the multipart boundary is effectively “free” from a quota perspective. Only the final chunk, the one containing the boundary, is counted.
The same pattern exists in `multipart_headers`, where `MoreRequiredForHeaders` also recurses without decrementing the quota.
As a result, an attacker can send arbitrarily large multipart bodies split across many chunks that avoid the boundary. The parser will accumulate the data (in memory for form fields, on disk for file uploads) without enforcing `max_body_size` or `max_files_size`.
### Impact
This is a denial of service vulnerability caused by uncontrolled resource consumption.
Any application using `require_form` or `require_multipart_form` on user-controlled input is affected. An unauthenticated attacker can send large multipart requests that bypass configured limits and cause:
- memory exhaustion (for form fields accumulated in memory)
- disk exhaustion (for file uploads written to temporary storage)
In both cases, the application may become unavailable or be terminated by the operating system.
### Workaround
Deploy a reverse proxy (such as nginx or HAProxy) in front of the application and enforce request body size limits there. This ensures large multipart requests are rejected before they reach the vulnerable parser.
### Resources
- Introducing commit: https://github.com/gleam-wisp/wisp/commit/d8e722e22ccb42bda9d0b6248658d37ab4e9b376
- Fix commit: https://github.com/gleam-wisp/wisp/commit/7a978748e12ab29db232c222254465890e1a4a90
A multipart form parsing bug allows any unauthenticated user to bypass configured request size limits and trigger a denial of service by exhausting server memory or disk.
### Details
The issue is in the multipart parsing logic, specifically in `multipart_body` and `multipart_headers`.
When parsing multipart data, the implementation distinguishes between:
- chunks where a boundary is found
- chunks where more data is required
In the normal case (boundary found), the parser correctly accounts for consumed bytes by calling `decrement_quota`.
However, in the `MoreRequiredForBody` branch, the parser appends incoming data to the output but recurses without decrementing the quota. This means that any chunk that does not contain the multipart boundary is effectively “free” from a quota perspective. Only the final chunk, the one containing the boundary, is counted.
The same pattern exists in `multipart_headers`, where `MoreRequiredForHeaders` also recurses without decrementing the quota.
As a result, an attacker can send arbitrarily large multipart bodies split across many chunks that avoid the boundary. The parser will accumulate the data (in memory for form fields, on disk for file uploads) without enforcing `max_body_size` or `max_files_size`.
### Impact
This is a denial of service vulnerability caused by uncontrolled resource consumption.
Any application using `require_form` or `require_multipart_form` on user-controlled input is affected. An unauthenticated attacker can send large multipart requests that bypass configured limits and cause:
- memory exhaustion (for form fields accumulated in memory)
- disk exhaustion (for file uploads written to temporary storage)
In both cases, the application may become unavailable or be terminated by the operating system.
### Workaround
Deploy a reverse proxy (such as nginx or HAProxy) in front of the application and enforce request body size limits there. This ensures large multipart requests are rejected before they reach the vulnerable parser.
### Resources
- Introducing commit: https://github.com/gleam-wisp/wisp/commit/d8e722e22ccb42bda9d0b6248658d37ab4e9b376
- Fix commit: https://github.com/gleam-wisp/wisp/commit/7a978748e12ab29db232c222254465890e1a4a90
nvd CVSS4.0
8.7
Vulnerability type
CWE-770
Allocation of Resources Without Limits
Published: 3 Apr 2026 · Updated: 3 Apr 2026 · First seen: 2 Apr 2026