CVE-2026-6855: Instructlab Path Traversal Vulnerability

HIGH
Advisory Identifier: GHSA-pqmg-c2j8-fq92
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CVSS 7.1
CWE-22
Published
Advisory Summary

CVE-2026-6855 is a HIGH (CVSS 7.1) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Instructlab libraries in the PyPI ecosystem. The issue involves instructlab vulnerable to path traversal. Remediation is available in the latest vendor maintenance releases.

CVE-2026-6855 at a Glance

CVE Identifier CVE-2026-6855
GHSA Identifier GHSA-pqmg-c2j8-fq92
Severity HIGH
CVSS v3.1 Base Score 7.1
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Instructlab
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-6855

To remediate this vulnerability, upgrade all affected Instructlab dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

instructlab fixed: Latest secure release 
pip install instructlab>=Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show instructlab

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-6855, inspect your installed packages using pip:

pip show instructlab

Analyze the terminal output to locate any version of Instructlab in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The pip show instructlab command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Instructlab, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A flaw was found in InstructLab. A local attacker could exploit a path traversal vulnerability in the chat session handler by manipulating the `logs_dir` parameter. This allows the attacker to create new directories and write files to arbitrary locations on the system, potentially leading to unauthorized data modification or disclosure.

CVE-2026-6855 Affected Instructlab Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
instructlab
pypi/instructlab
PyPI
≤ 0.26.1

References

NVD — CVE-2026-6855 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6855
Instructlab Security Information SECURITY
https://access.redhat.com/security/cve/CVE-2026-6855
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=2460013
Instructlab Source Repository REPOSITORY
https://github.com/instructlab/instructlab

Frequently Asked Questions

What is CVE-2026-6855?
CVE-2026-6855 is a security vulnerability in Instructlab involving InstructLab vulnerable to Path Traversal under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Instructlab versions are affected?
Affected versions include releases prior to current release patches across affected packages: instructlab.
What version fixes CVE-2026-6855?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is instructlab affected?
Yes, instructlab is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-6855?
CVE-2026-6855 has a CVSS v3.1 base score of 7.1 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-6855?
CVE-2026-6855 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check PyPI dependencies for CVE-2026-6855?
Run the dependency tree command: 'pip show instructlab'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-pqmg-c2j8-fq92",
  "modified" : "2026-04-29T22:02:43Z",
  "published" : "2026-04-22T15:31:40Z",
  "aliases" : [ "CVE-2026-6855" ],
  "summary" : "InstructLab vulnerable to Path Traversal",
  "details" : "A flaw was found in InstructLab. A local attacker could exploit a path traversal vulnerability in the chat session handler by manipulating the `logs_dir` parameter. This allows the attacker to create new directories and write files to arbitrary locations on the system, potentially leading to unauthorized data modification or disclosure.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "instructlab"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.26.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-6855"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/security/cve/CVE-2026-6855"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2460013"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/instructlab/instructlab"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-29T22:02:43Z",
    "nvd_published_at" : "2026-04-22T13:16:22Z"
  }
}