MicroPython: Use After Free
CVE-2023-7152 is a critical-severity use after free vulnerability in MicroPython, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected MicroPython versions: 1.21.0; 1.22.0-preview. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.89% chance of exploitation within 30 days, higher than 60% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of MicroPython you run against the affected versions below, and install the vendor's latest release.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| MicroPython | MicroPython | 1.21.0; 1.22.0-preview | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 5.5 | Medium | CNA (vuldb.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 2.0 | 5.2 | Medium | CNA (vuldb.com) |
Official description
A vulnerability, which was classified as critical, has been found in MicroPython 1.21.0/1.22.0-preview. Affected by this issue is the function poll_set_add_fd of the file extmod/modselect.c. The manipulation leads to use after free. The exploit has been disclosed to the public and may be used. The patch is identified as 8b24aa36ba978eafc6114b6798b47b7bfecdca26. It is recommended to apply a patch to fix this issue. VDB-249158 is the identifier assigned to this vulnerability.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Third-party and government advisories
- vuldb.com/?ctiid.249158Permissions Required, Third Party Advisory, VDB Entry
- vuldb.com/?id.249158Third Party Advisory, VDB Entry
Technical write-ups (may include proof of concept)
- github.com/micropython/micropython/issues/12887Exploit, Issue Tracking
Other references
Other vulnerabilities in MicroPython
- 7.5 High severity
- 8.1 High severity
- 7.5 High severity
- 9.8 Critical severity
Recent Use After Free vulnerabilities
- 7.0 High severity
- 8.8 High severity
- 8.8 High severity
- 7.8 High severity
- 8.8 High severity
- 8.8 High severity
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