CVE-2022-41956

Executive Summary

CVE-2022-41956 is a file disclosure vulnerability in Autolab, a web-based course management service developed at Carnegie Mellon University that enables instructors to offer autograded programming assignments. The flaw exists in the remote handin feature, allowing authenticated users to submit assignments using file paths outside their designated submission directory, and subsequently view the submitted files to read their contents. The vulnerability affects Autolab versions prior to 2.10.0, has a CVSS score of 6.5, and could allow students or other users with access to the handin functionality to read arbitrary files accessible to the Autolab process on the underlying server.

Technical Analysis

Autolab is a course management platform that provides autograding and assignment submission capabilities. The remote handin feature allows users to reference files from a remote location when submitting assignments, giving instructors the ability to configure a server-side path from which students can pull assignment files. The vulnerability arises from insufficient validation of user-supplied paths used during the handin process.

The NVD description indicates that the remote handin feature does not restrict users to their submission directory. A user can craft a handin request that references a file path outside the intended submission directory boundary — for example, using relative path traversal sequences or absolute paths to other locations on the filesystem. When the user subsequently views the submission, the application renders the content of the referenced file back to the user, thereby disclosing the file's contents.

The technical mechanism at play is a path traversal or path validation flaw. The application fails to canonicalize and verify that the resolved path stays within the allowed submission directory. Since the workaround specifically warns against running Autolab as root (or any user with write access to /), this confirms the vulnerability is exploitable against the filesystem that the Autolab service process has read access to. If Autolab runs with elevated privileges or as a service account with broad filesystem access, the blast radius increases significantly — an attacker could potentially read configuration files, source code, credentials, or other sensitive data stored on the server.

The patch in version 2.10.0 addresses the path validation logic, and the vendor provides two workarounds: (1) leave the remote handin path field empty (Edit Assessment > Advanced > Remote handin path), and (2) disable the feature entirely by replacing the body of local_submit in app/controllers/assessment/handin.rb with render(plain: "Feature disabled", status: :bad_request) && return.

Insufficient technical detail is available in the NVD description to enumerate exact function names, URL parameters, or API endpoints beyond those mentioned. The vulnerability is confirmed to affect only the remote handin feature, and exploitation requires the ability to submit a handin with a crafted path.

Exploitation Scenarios

Step 1 — Reconnaissance/Target Identification: An attacker must first identify an Autolab instance that has the remote handin feature enabled. This requires being a registered user within a course that uses Autolab (e.g., a student). The attacker would locate the assessment page that supports remote handin by inspecting the submitted file form or by reviewing the assessment configuration.

Step 2 — Flaw Trigger: During submission, the attacker does not provide a regular filename, but instead supplies a path that traverses outside the submission directory. This could be an absolute path like /etc/passwd or a relative traversal path such as ../../../../etc/passwd. The vulnerable backend code does not validate that the resolved path remains inside the intended submission directory.

Step 3 — Payload/Execution at Vulnerability-Class Level: At the vulnerability-class level, this is a path traversal leading to arbitrary file read. The attacker submits a handin referencing a sensitive file on the server filesystem. The application resolves the path and stores or displays it. Because the remote handin feature is designed to pull files from a configured remote path, the file fetching mechanism does not enforce confinement to the submission directory.

Step 4 — Post-Exploitation Impact: After submission, the attacker views the submission through the normal submission-viewing interface. The contents of the referenced file are rendered to the attacker. The attacker can then iterate over common sensitive file locations — configuration files, environment files, application source code, credential stores, or other users' submissions — to map out the server's filesystem and extract sensitive data.

No public PoC is available; this attack chain is inferred from the vulnerability class (arbitrary file read via path traversal) and the NVD description.

Impact Assessment

The CVSS score of 6.5 reflects a medium-severity vulnerability. The primary impact is confidentiality — an attacker can read arbitrary files on the server that are accessible to the Autolab process. The integrity and availability impact is limited, as the vulnerability is a file disclosure flaw rather than a code execution or data modification issue.

Affected Systems: Any Autolab deployment running version prior to 2.10.0 with the remote handin feature enabled.

Business Impact: For a university or educational institution, the risk includes exposure of:

• Server configuration files (database credentials, API keys, secrets)
• Application source code
• Other students' submission data (potentially containing academic integrity violations, personal information)
• Operating system files (e.g., /etc/passwd which enumerates user accounts)

Attack Prerequisites: The attacker must be an authenticated user with access to an assessment that uses the remote handin feature. This lowers the barrier to entry since any enrolled student in a course using Autolab can potentially exploit it.

Blast Radius: If Autolab is running as root — a scenario explicitly warned against in the vendor's workaround — the entire filesystem is exposed. Even in a least-privilege configuration, the Autolab process typically has access to the application directory, database configuration, and potentially other services on the host.

Detection Guidance

Sigma Rule

title: Autolab Remote Handin Path Traversal
id: 3b6f7c9e-2a11-4f5d-9b0e-6c6a51c9d42f
status: experimental
description: Detects suspicious file paths in Autolab handin submissions indicative of path traversal attempt CVE-2022-41956
author: Valtersit Threat Intel
logsource:
  category: webserver
  product: apache
  definition: 'Monitor access logs of Autolab handin submission endpoints'
detection:
  selection:
    cs-uri-query|contains:
      - '..%2f'
      - '..%5c'
      - 'handin_path='
      - 'remote_path='
  filter:
    cs-uri-query|contains:
      - '/var/tmp/'
      - '/usr/share/'
      - 'upload'
  condition: selection and not filter
level: high

YARA Rule

rule Autolab_Handin_PathTraversal {
    meta:
        author = "Valtersit Threat Intel"
        description = "Detects path traversal patterns in Autolab remote handin requests"
        cve = "CVE-2022-41956"
        date = "2025-01-27"
        score = 60

    strings:
        $a = "remote_handin"
        $b = "handin_path"
        $c = "../"
        $d = "..\\"
        $e = "local_submit"
        $f = "assessment/handin"

    condition:
        ($a or $b or $e or $f) and ($c or $d)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2022-41956 - Autolab Remote Handin Path Traversal Attempt"; flow:established,to_server; content:"POST"; http_method; content:"handin"; http_uri; nocase; content:".."; http_uri; distance:0; pcre:"/(\.\.(\/|%2f|\\|%5c)){2,}/Ui"; classtype:attempted-recon; sid:20220041956; rev:1;)

Elastic Detection

sequence by process.entity_id with maxspan=10s
  [http where request.method == "POST" and
   url.path like "*handin*" and
   (url.query like "*..%2f*" or url.query like "*..%5c*" or
    url.query like "*../*" or url.query like "*..\\*")]

file where event.action in ("open", "read") and
  file.path like "*" and
  process.executable is not null and
  stringLength(file.path) > 0

Splunk SPL Query

index=web sourcetype=access_combined status>=200
| regex uri="(\.\.(\/|%2f|\\|%5c)){2,}"
| search uri="*handin*"
| table _time, src_ip, uri, http_user_agent, session_id
| sort - _time
| rename src_ip as source_address, uri as request_uri

Wazuh OSSEC Rule

<group name="autolab,">
  <rule id="100419" level="12">
    <decoded>pattern: ../</decoded>
    <match>handin</match>
    <regex>\.\./</regex>
    <description>Autolab path traversal attempt detected in handin request (CVE-2022-41956)</description>
    <mitre>
      <id>T1083</id>
    </mitre>
    <group>web_application_attack,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 3/4 (LIKELY — 2 independent sources confirm fix: CNA and OSV)

Immediate Mitigations:

1. Leave the remote handin path field empty (Edit Assessment > Advanced > Remote handin path) for all assessments.
2. Do not run Autolab as root or any user with write access to /. Run it as a least-privilege service account with access only to the directories required for function.
3. If the remote handin feature is not needed, disable it by replacing the body of local_submit in app/controllers/assessment/handin.rb with render(plain: "Feature disabled", status: :bad_request) && return.

Patch/Upgrade Steps:

1. Upgrade Autolab to version 2.10.0 or later, which contains the official fix for this vulnerability.
2. After upgrading, verify that the path validation logic restricts remote handin paths to the intended submission directory.
3. Test the remote handin functionality in a staging environment before full production deployment.

Long-Term Hardening:

1. Implement file path canonicalization and validation at the application layer — ensure resolved paths are prefixed with the intended base directory.
2. Run periodic security audits of Autolab deployments, focusing on input validation and path traversal vectors.
3. Monitor server logs for unusual handin requests containing path traversal patterns.
4. Follow the principle of least privilege for the Autolab service account.
5. Subscribe to Autolab security advisories to receive prompt notification of future vulnerabilities.

References

1. NVD Entry for CVE-2022-41956: https://nvd.nist.gov/vuln/detail/CVE-2022-41956
2. OSV Database Entry for CVE-2022-41956: https://osv.dev/vulnerability/CVE-2022-41956
3. Autolab Project (GitHub): https://github.com/autolab/Autolab
4. CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — Not listed (no evidence of exploitation in the wild)

Additional Intel Assessment: As of this report, there is no public PoC or evidence of active exploitation of CVE-2022-41956 in the wild. The EPSS score of 0.01768 (76.1% percentile) suggests a moderate likelihood of exploitation relative to other known CVEs. No known threat actor campaigns have been attributed to this vulnerability. The vulnerability requires authenticated access to an Autolab instance, limiting its exposure to those who are already enrolled in a course using the platform. Nevertheless, given the prevalence of Autolab in academic environments and the sensitive nature of the data potentially exposed, prompt patching is strongly recommended.