PYSEC-2024-38 CVE-2024-24762 GHSA-2jv5-9r88-3w3p GHSA-qf9m-vfgh-m389 PYSEC-2026-1850
python-multipart vulnerable to Content-Type Header ReDoS
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 1.52%
- Chance of exploitation in the next 30 days. Higher than 74.64% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Fix
- Available
- 2 packages have a fixed version
Description
FastAPI is a web framework for building APIs with Python 3.8+ based on standard Python type hints. When using form data, python-multipart uses a Regular Expression to parse the HTTP Content-Type header, including options. An attacker could send a custom-made Content-Type option that is very difficult for the RegEx to process, consuming CPU resources and stalling indefinitely (minutes or more) while holding the main event loop. This means that process can't handle any more requests. It's a ReDoS(Regular expression Denial of Service), it only applies to those reading form data, using python-multipart. This vulnerability has been patched in version 0.109.1.
Affected versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| fastapi | <= 0.109.0 |
No fix yet |
| fastapi | < 0.109.1 |
0.109.1 |
| fastapi | < 0.109.1 |
0.109.1 |
| python-multipart | <= 0.0.6 |
No fix yet |
| python-multipart | < 0.0.7 |
0.0.7 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
fastapi PyPI → 0.109.1
- pip
pip install --upgrade "fastapi>=0.109.1"- poetry
poetry add "fastapi>=0.109.1"- uv
uv add "fastapi>=0.109.1"
python-multipart PyPI → 0.0.7
- pip
pip install --upgrade "python-multipart>=0.0.7"- poetry
poetry add "python-multipart>=0.0.7"- uv
uv add "python-multipart>=0.0.7"
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-1333: Inefficient Regular Expression Complexity
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
How to prevent it
- Architecture and Design: Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
- System Configuration: Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
- Implementation: Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
- Implementation: Limit the length of the input that the regular expression will process.
CWE-400: Uncontrolled Resource Consumption
The product does not properly control the allocation and maintenance of a limited resource.
How to prevent it
- Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
- Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. 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.
- Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
- Implementation: Ensure that all failures in resource allocation place the system into a safe posture.
References
Advisories
- github.com/advisories/GHSA-2jv5-9r88-3w3p
- github.com/Kludex/python-multipart/security/advisories/GHSA-2jv5-9r88-3w3p
- nvd.nist.gov/vuln/detail/CVE-2024-24762
- github.com/advisories/GHSA-qf9m-vfgh-m389
- github.com/tiangolo/fastapi/security/advisories/GHSA-qf9m-vfgh-m389
- github.com/encode/starlette/security/advisories/GHSA-93gm-qmq6-w238
Fixes and patches
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-8h2j-cgx8-6xv7 Cross-Site Request Forgery (CSRF) in FastAPI | High | Also affects fastapi |
| GHSA-7wch-p9px-956x Forge: Regular expression denial of service in PEM decoding (pem.decode) | High | Same weakness, CWE-1333 |
| GHSA-xcq7-p3pf-p88h OpenTelemetry Python: Unbounded tracestate parsing in opentelemetry-api | Medium | Same weakness, CWE-1333 |
| GHSA-xgh8-jp6q-p5x8 Pillow: ReDoS in XbmImagePlugin: 512-byte file stalls Image.open() for minutes | High | Same weakness, CWE-1333 |
| GHSA-rxp7-6hxx-x8q5 ip-address: Address6 matches a zone identifier in quadratic time ahead of its length limit, allowing a single long string to stall the process | Medium | Same weakness, CWE-1333 |
| GHSA-r925-mgvr-h9cc Symfony: ReDoS in HeaderUtils::split() Reachable Through the Cache-Control Request Header | High | Same weakness, CWE-1333 |
| GHSA-4ffr-jq9g-5ffx Nodemailer: Quadratic backtracking in SMTP AUTH mechanism detection regexes allows pre-auth remote denial of service | High | Same weakness, CWE-1333 |
| GHSA-m64x-33q8-m5h7 GitPython parse_actor_and_date() is vulnerable to quadratic backtracking on malformed identity lines | High | Same weakness, CWE-1333 |
Credits: Kludex, amita-seal, garyd203, huonw, levpachmanov, nicecatch2000
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