Crow: Use After Free
CVE-2022-38667 is a critical-severity use after free vulnerability in Crow from CrowCpp, 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 Crow versions: 1.0\+4 and earlier. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 3.22% chance of exploitation within 30 days, higher than 88% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of Crow 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
Version data comes from NVD's product matching. 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.
Official description
HTTP applications (servers) based on Crow through 1.0+4 may allow a Use-After-Free and code execution when HTTP pipelining is used. The HTTP parser supports HTTP pipelining, but the asynchronous Connection layer is unaware of HTTP pipelining. Specifically, the Connection layer is unaware that it has begun processing a later request before it has finished processing an earlier request.
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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.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
- github.com/CrowCpp/Crow/pull/524Third Party Advisory
Third-party and government advisories
- cwe.mitre.org/data/definitions/372.htmlTechnical Description, Third Party Advisory
Technical write-ups (may include proof of concept)
- github.com/0xhebi/CVEs/blob/main/Crow/CVE-2022-38667.mdExploit, Third Party Advisory
- gynvael.coldwind.pl/?id=753Exploit, Third Party Advisory
Other vulnerabilities in Crow
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
Recent Use After Free vulnerabilities
- 9.8 Critical severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
- 8.8 High severity
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