CVE-2023-38545
Description
A heap-based buffer overflow flaw was found in the SOCKS5 proxy handshake in the Curl package. If Curl is unable to resolve the address itself, it passes the hostname to the SOCKS5 proxy. However, the maximum length of the hostname that can be passed is 255 bytes. If the hostname is longer, then Curl switches to the local name resolving and passes the resolved address only to the proxy. The local variable that instructs Curl to "let the host resolve the name" could obtain the wrong value during a slow SOCKS5 handshake, resulting in the too-long hostname being copied to the target buffer instead of the resolved address, which was not the intended behavior.
Statement
This flaw does not affect the versions of curl as shipped with Red Hat Enterprise Linux 6, 7, and 8.
An overflow is only possible in applications that do not set CURLOPT_BUFFERSIZE, or set it smaller than approximately 65kB. Since the curl tool sets CURLOPT_BUFFERSIZE to 100kB by default, it is not vulnerable unless rate limiting was set by the user to a size smaller than 65kB.
Knowledgebase article:
Mitigation
To avoid this issue, we recommend you do not use `CURLPROXY_SOCKS5_HOSTNAME` proxies with curl. Also do not set a proxy environment variable to socks5h://
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.1 | 9.8 | 8.8 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | Required |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
Since the curl tool sets CURLOPT_BUFFERSIZE to 100kB by default, it is not vulnerable unless rate limiting was set by the user to a size smaller than 65kB.
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands; Modify Memory
If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow. If the attacker can overwrite a pointer's worth of memory (usually 32 or 64 bits), they can alter the intended control flow by redirecting a function pointer to their own malicious code. Even when the attacker can only modify a single byte arbitrary code execution can be possible. Sometimes this is because the same problem can be exploited repeatedly to the same effect. Other times it is because the attacker can overwrite security-critical application-specific data -- such as a flag indicating whether the user is an administrator.
Availability,Confidentiality
Technical Impact: Read Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
Out of bounds memory access will very likely result in the corruption of relevant memory, and perhaps instructions, possibly leading to a crash. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
Confidentiality
Technical Impact: Read Memory
In the case of an out-of-bounds read, the attacker may have access to sensitive information. If the sensitive information contains system details, such as the current buffer's position in memory, this knowledge can be used to craft further attacks, possibly with more severe consequences.
Acknowledgements
Red Hat would like to thank Jay Satiro for reporting this issue.
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