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remote code execution via git repo provider

Critical severity GitHub Reviewed Published Aug 25, 2021 in jupyterhub/binderhub • Updated Sep 13, 2024

Package

pip binderhub (pip)

Affected versions

< 0.2.0

Patched versions

0.2.0

Description

Impact

A remote code execution vulnerability has been identified in BinderHub, where providing BinderHub with maliciously crafted input could execute code in the BinderHub context, with the potential to egress credentials of the BinderHub deployment, including JupyterHub API tokens, kubernetes service accounts, and docker registry credentials. This may provide the ability to manipulate images and other user created pods in the deployment, with the potential to escalate to the host depending on the underlying kubernetes configuration.

Patches

Patch below, or on GitHub

From 9f4043d9dddc1174920e687773f27b7933f48ab6 Mon Sep 17 00:00:00 2001
From: Riccardo Castellotti <rcastell@cern.ch>
Date: Thu, 19 Aug 2021 15:49:43 +0200
Subject: [PATCH] Explicitly separate git-ls-remote options from positional
 arguments

---
 binderhub/repoproviders.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/binderhub/repoproviders.py b/binderhub/repoproviders.py
index f33347b..5d4b87c 100755
--- a/binderhub/repoproviders.py
+++ b/binderhub/repoproviders.py
@@ -484,7 +484,7 @@ class GitRepoProvider(RepoProvider):
             self.sha1_validate(self.unresolved_ref)
         except ValueError:
             # The ref is a head/tag and we resolve it using `git ls-remote`
-            command = ["git", "ls-remote", self.repo, self.unresolved_ref]
+            command = ["git", "ls-remote", "--", self.repo, self.unresolved_ref]
             result = subprocess.run(command, universal_newlines=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             if result.returncode:
                 raise RuntimeError("Unable to run git ls-remote to get the `resolved_ref`: {}".format(result.stderr))
-- 
2.25.1

Workarounds

Disable the git repo provider by specifying the BinderHub.repo_providers config, e.g.:

from binderhub.repoproviders import (GitHubRepoProvider,
                            GitLabRepoProvider, GistRepoProvider,
                            ZenodoProvider, FigshareProvider, HydroshareProvider,
                            DataverseProvider)

c.BinderHub.repo_providers =  {
            'gh': GitHubRepoProvider,
            'gist': GistRepoProvider,
            'gl': GitLabRepoProvider,
            'zenodo': ZenodoProvider,
            'figshare': FigshareProvider,
            'hydroshare': HydroshareProvider,
            'dataverse': DataverseProvider,
        }

References

Credit: Jose Carlos Luna Duran (CERN) and Riccardo Castellotti (CERN).

For more information

If you have any questions or comments about this advisory:

References

@minrk minrk published to jupyterhub/binderhub Aug 25, 2021
Reviewed Aug 25, 2021
Published by the National Vulnerability Database Aug 25, 2021
Published to the GitHub Advisory Database Aug 30, 2021
Last updated Sep 13, 2024

Severity

Critical

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 Passive
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality High
Integrity High
Availability High

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:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

EPSS score

0.722%
(80th percentile)

Weaknesses

CVE ID

CVE-2021-39159

GHSA ID

GHSA-9jjr-qqfp-ppwx

Source code

Credits

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