CVE-2026-82331

Description

Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache BuildStream running on Python < 3.12 allows malicious source tarballs to write files on the host, with the privileges of the user running BuildStream, via symlinks as part of source fetching. The impact of this issue is mitigated by: * BuildStream projects should only use trusted sources in their elements as otherwise the build output can also not be trusted * Tracking a source tarball pins its SHA256 hash, which prevents MITM attacks of users that are fetching an already tracked project * When running on Python >= 3.12, BuildStream >= 2.3.0 already makes use of the Python `tarfile` filter functionality, which blocks the symlink escape Users are recommended to upgrade to version 2.8.1, which fixes this issue.

Overview

State: PUBLISHED
Assigner (CNA): apache
CVSS severity: —
CVSS score: —
CVSS vector: —
Effective score: 9.8 / 10 CRITICAL source: NVD
CWE(s): CWE-59
Reserved: 2026-08-28
Published: 2026-09-23 06:58 UTC
Last updated: 2026-09-23 16:08 UTC
Source: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/82xxx/CVE-2026-82331.json

NVD triage scoring NVD CVE 2.0

Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.

NVD published: 2026-09-23 07:16:46 UTC
NVD last modified: 2026-09-23 17:58:26 UTC
NVD CVSS v3.1: 9.8 / 10 CRITICAL source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
NVD CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Exploitability subscore: 3.9 / 10
Impact subscore: 5.9 / 10
EPSS score: 0.0019 (probability of exploitation in next 30 days)
EPSS percentile: 9.54% vs all CVEs — higher = more likely to be exploited, as of 2026-09-23

European Union Vulnerability Database ENISA EUVD

ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.

EUVD ID: EUVD-2026-85113
Assigner: apache
Published: Sep 23, 2026, 6:58:21 AM
Updated: Sep 23, 2026, 4:08:58 PM
EUVD base score (CVSS 3.1): 9.8 / 10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EUVD-reported EPSS: 0.2000
Vendors: Apache Software Foundation
Products: Apache BuildStream (0 ≤2.8.0)
Aliases: GHSA-5xjv-h9hc-3vv9

ENISA description: Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache BuildStream running on Python < 3.12 allows malicious source tarballs to write files on the host, with the privileges of the user running BuildStream, via symlinks as part of source fetching. The impact of this issue is mitigated by: * BuildStream projects should only use trusted sources in their elements as otherwise the build output can also not be trusted * Tracking a source tarball pins its SHA256 hash, which prevents MITM attacks of users that are fetching an already tracked project * When running on Python >= 3.12, BuildStream >= 2.3.0 already makes use of the Python `tarfile` filter functionality, which blocks the symlink escape Users are recommended to upgrade to version 2.8.1, which fixes this issue.

EUVD references (1)

https://lists.apache.org/thread/9b342631x7bvtyg0pq7zgywtl2cmy34v

Affected products (1)

Vendor	Product	Versions	Platforms
Apache Software Foundation	Apache BuildStream	`0` (affected), `2.8.1` (unaffected)	—

Vendor references (1)

References embedded in the original CVE record by the assigning CNA.

https://lists.apache.org/thread/9b342631x7bvtyg0pq7zgywtl2cmy34v vendor-advisory

Web references (0)

DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.

No web references attached yet.

NVD-tagged references (2)

Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.

http://www.openwall.com/lists/oss-security/2026/09/23/9 af854a3a-2127-422b-91ae-364da2661108
https://lists.apache.org/thread/9b342631x7bvtyg0pq7zgywtl2cmy34v security@apache.org

Remediations (10)

CVE-2026-82331 - Apache BuildStream: tar source extraction escape

web:cvefeed.io

The following list is the news that have been mention CVE-2026-82331 vulnerability anywhere in the article. Results are limited to the first 20 news articles due to potential performance issues. The following table lists the changes that have been made to the CVE-2026-82331 vulnerability over time.

2026-09-24 11:50 UTC
CVE-2026-82331: Apache BuildStream Link Following - CVETodo

web:cvetodo.com

CVE-2026-82331 is a CVSS 9.8 Link Following vulnerability in Apache BuildStream. See exploitation status, patch guidance, and technical details.

2026-09-24 11:50 UTC
Microsoft Patch Tracker (September 2026): Exploit-Ranked | Senserva

web:senserva.com

Every Microsoft security patch (KB) and the CVEs it fixes, with severity, CVSS, and CISA KEV status. Cross-linked to the CVE reference.

2026-09-24 11:50 UTC
SAP Security Patch Day - May 2026

web:support.sap.com

SAP security Patch Day Bulletin This post shares the information on security notes that remediate vulnerabilities discovered in SAP products. SAP strongly recommends that the customer visits the support portal and applies patches on priority to protect their SAP landscape. On 12 th of May 2026 , SAP security patch day saw the release of 15 new security notes.

2026-09-24 11:50 UTC
CVE-2026-82331 | Ubuntu

web:ubuntu.com

Description Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache BuildStream running on Python < 3.12 allows malicious source tarballs to write files on the host, with the privileges of the user running BuildStream, via symlinks as part of source fetching. The impact of this issue is mitigated by: * BuildStream projects should only ...

2026-09-24 11:50 UTC
What Is CVE Remediation in 2026? - aikido.dev

web:www.aikido.dev

CVE remediation is fixing known flaws in the software you run. Why upgrading often fails, what remediation actually involves, and how backporting fixes it.

2026-09-24 11:50 UTC
Oracle Critical Patch Update Advisory - July 2026

web:www.oracle.com

This Critical Patch Update contains 1448 new security patches across the product families listed below. Please note that a My Oracle Support (MOS) note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at July 2026 Critical Patch Update: Executive Summary and Analysis.

2026-09-24 11:50 UTC
Oracle Critical Security Patch Update Advisory - June 2026

web:www.oracle.com

Additional CVEs addressed are: The patch for CVE - 2026 -34481 also addresses CVE - 2026 -34477, CVE - 2026 -34478, CVE - 2026 -34479, and CVE - 2026 -34480. Oracle Fusion Middleware Risk Matrix This Critical Security Patch Update contains 106 new security patches for Oracle Fusion Middleware. 53 of these vulnerabilities may be remotely exploitable without authentication, i.e., may be exploited over a ...

2026-09-24 11:50 UTC
CVE-2026-82331: Apache Software Foundation Apache BuildStream ... - Rapid7

web:www.rapid7.com

CVE-2026-82331 : Apache Software Foundation Apache BuildStream: Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache…. View severity, references, and remediation details from Rapid7.

2026-09-24 11:50 UTC
CVE-2026-82331 | Tenable®

web:www.tenable.com

Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache BuildStream running on Python < 3.12 allows malicious source tarballs to write files on the host, with the privileges of the user running BuildStream, via symlinks as part of source fetching. The impact of this issue is mitigated by: * BuildStream projects should only use trusted ...

2026-09-24 11:50 UTC

AI Forensic Analysis

Only Available for Registered Users. Sign in to view.

Raw JSON

The full cvelistV5 record. Download as CVE-2026-82331.json.

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 9.8,
              "baseSeverity": "CRITICAL",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "HIGH",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-82331",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-23T14:55:37.367789Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-23T14:55:54.267Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      },
      {
        "providerMetadata": {
          "dateUpdated": "2026-09-23T16:08:58.171Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/09/23/9"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://pypi.python.org",
          "defaultStatus": "unaffected",
          "packageName": "buildstream",
          "packageURL": "pkg:pypi/BuildStream",
          "product": "Apache BuildStream",
          "vendor": "Apache Software Foundation",
          "versions": [
            {
              "lessThanOrEqual": "2.8.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "2.8.1",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Gjoko Krstic of Zero Science Lab"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache BuildStream running on Python &lt; 3.12 allows malicious source tarballs to write files on the host, with the privileges of the user running BuildStream, via symlinks as part of source fetching.<br><div>The impact of this issue is mitigated by:</div>* BuildStream projects should only use trusted sources in their elements as otherwise the build output can also not be trusted<br>* Tracking a source tarball pins its SHA256 hash, which prevents MITM attacks of users that are fetching an already tracked project<br>* When running on Python &gt;= 3.12, BuildStream &gt;= 2.3.0 already makes use of the Python `tarfile` filter functionality, which blocks the symlink escape<br><br>Users are recommended to upgrade to version 2.8.1, which fixes this issue."
            }
          ],
          "value": "Improper link resolution before file access ('link following') vulnerability in the `tar` source plugin of Apache BuildStream running on Python < 3.12 allows malicious source tarballs to write files on the host, with the privileges of the user running BuildStream, via symlinks as part of source fetching.\nThe impact of this issue is mitigated by:\n\n* BuildStream projects should only use trusted sources in their elements as otherwise the build output can also not be trusted\n* Tracking a source tarball pins its SHA256 hash, which prevents MITM attacks of users that are fetching an already tracked project\n* When running on Python >= 3.12, BuildStream >= 2.3.0 already makes use of the Python `tarfile` filter functionality, which blocks the symlink escape\n\nUsers are recommended to upgrade to version 2.8.1, which fixes this issue."
        }
      ],
      "metrics": [
        {
          "other": {
            "content": {
              "text": "moderate"
            },
            "type": "Textual description of severity"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-59",
              "description": "CWE-59 Improper link resolution before file access ('link following')",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-23T06:58:21.546Z",
        "orgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
        "shortName": "apache"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://lists.apache.org/thread/9b342631x7bvtyg0pq7zgywtl2cmy34v"
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "Apache BuildStream: tar source extraction escape",
      "x_generator": {
        "engine": "Vulnogram 1.0.3"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f0158376-9dc2-43b6-827c-5f631a4d8d09",
    "assignerShortName": "apache",
    "cveId": "CVE-2026-82331",
    "datePublished": "2026-09-23T06:58:21.546Z",
    "dateReserved": "2026-08-28T14:59:00.996Z",
    "dateUpdated": "2026-09-23T16:08:58.171Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}