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copyparty vulnerable to path traversal attack

High severity GitHub Reviewed Published Jul 14, 2023 in 9001/copyparty • Updated Sep 13, 2024

Package

pip copyparty (pip)

Affected versions

< 1.8.2

Patched versions

1.8.2

Description

Summary

All versions before 1.8.2 have a path traversal vulnerability, allowing an attacker to download unintended files from the server.

Details

Unauthenticated users were able to retrieve any files which are accessible (according to OS-level permissions) from the copyparty process. Usually, this is all files that are readable by the OS account which is used to run copyparty.

The vulnerability did not make it possible to list the contents of folders, so an attacker needs to know the full absolute path to the file, or the relative path from where copyparty is installed.

Some methods of running copyparty (prisonparty, the nix package, and docker) had a mitigating effect, mostly reducing the attack scope to files inside copyparty volumes, and possibly the copyparty config file.

Checking for attacks

Please keep in mind that, if an attacker were to find a way to overwrite the logs, for example by discovering the password to another service with sufficient privileges, then the following approaches cannot be trusted.

if copyparty was only accessible through a reverse proxy, then all attacks would be visible in the webserver access-log as URLs which contain both .cpr/ and %2F

  • nginx: 
    (gzip -dc access.log*.gz; cat access.log) | sed -r 's/" [0-9]+ .*//' | grep -E 'cpr/.*%2[^0]' | grep -vF data:image/svg

However, if copyparty was directly accessible from the internet, then any successful attacks (file retrievals) would unfortunately leave no trace. That said, it is very probable that an attacker would make at least one invalid attempt, which would become apparent in the copyparty server log, detectable with grep -aE '(Errno|Permission).*\.cpr/' revealing the following:

  • python2 example: [IOError] [Errno 13] Permission denied: '/etc/shadow', .cpr//etc/shadow
  • python3 example: [PermissionError] [Errno 13] Permission denied: b'/etc/shadow', .cpr//etc/shadow

Providing an exact command for this approach is difficult, as it depends on how copyparty is deployed;

  • if copyparty was running as a systemd service: journalctl -am | grep -aE '(Errno|Permission).*\.cpr/'
  • if copyparty was logging to a compressed file: xz -kdc thefilename.xz | grep -aE '(Errno|Permission).*\.cpr/'
  • if the copyparty log is available in a plaintext file: grep -aE '(Errno|Permission).*\.cpr/' thefilename.txt

PoC / attack example

curl -sik http://127.0.0.1:3923/.cpr/%2Fetc%2Fpasswd
curl -sik http://127.0.0.1:3923/.cpr/..%2F..%2F..%2F..%2F..%2Fetc%2Fpasswd

References

@9001 9001 published to 9001/copyparty Jul 14, 2023
Published by the National Vulnerability Database Jul 14, 2023
Published to the GitHub Advisory Database Jul 14, 2023
Reviewed Jul 14, 2023
Last updated Sep 13, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

6.985%
(94th percentile)

Weaknesses

CVE ID

CVE-2023-37474

GHSA ID

GHSA-pxfv-7rr3-2qjg

Source code

Credits

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