CVE-2026-33858: Apache Airflow Unsafe Deserialization Vulnerability

HIGH
Advisory Identifier: GHSA-mc4f-r875-v87w
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CVSS 8.8
CWE-502
Published
Advisory Summary

CVE-2026-33858 is a HIGH (CVSS 8.8) unsafe deserialization vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Apache Airflow libraries in the PyPI ecosystem. The issue involves unsafe deserialization via legacy serialization keys (__type/__var) bypass in xcom api. Remediation is available by upgrading affected packages to version 3.2.0.

CVE-2026-33858 at a Glance

CVE Identifier CVE-2026-33858
GHSA Identifier GHSA-mc4f-r875-v87w
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Apache Airflow
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 8.8

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

Attack Vector Network (AV:N)
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 High (A:H)

How to Fix CVE-2026-33858

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

apache-airflow fixed: 3.2.0 
pip install apache-airflow>=3.2.0
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 apache-airflow

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-33858, inspect your installed packages using pip:

pip show apache-airflow

Analyze the terminal output to locate any version of Apache Airflow in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.2.0), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. In Apache Airflow, 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

Dag Authors, who normally should not be able to execute code in the webserver context could craft XCom payload causing the webserver to execute arbitrary code. Since Dag Authors are already highly trusted, severity of this issue is Low. Users are recommended to upgrade to Apache Airflow 3.2.0, which resolves this issue.

CVE-2026-33858 Affected Apache Airflow Versions

1 component(s)
Fixed Versions:
3.2.0
Product / Package Ecosystem Affected Versions Fixed Version
apache-airflow
pypi/apache-airflow
PyPI
≥ 3.1.8
< 3.2.0
3.2.0

References

NVD — CVE-2026-33858 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33858
Apache Airflow Source Repository REPOSITORY
https://github.com/apache/airflow/pull/64148
Apache Airflow Source Repository REPOSITORY
https://github.com/apache/airflow
Apache Airflow Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/apache-airflow/PYSEC-2026-20.yaml
lists.apache.org/thread/1npt3o2x81s0... WEB
https://lists.apache.org/thread/1npt3o2x81s0gw9tmfcv4n7p1z9hdmy0
Apache Airflow Security Information SECURITY
http://www.openwall.com/lists/oss-security/2026/04/13/7

Frequently Asked Questions

What is CVE-2026-33858?
CVE-2026-33858 is a security vulnerability in Apache Airflow involving Unsafe Deserialization via Legacy Serialization Keys (__type/__var) Bypass in XCom API under CWE-502: Deserialization of Untrusted Data.
Which Apache Airflow versions are affected?
Affected versions include releases prior to 3.2.0 across affected packages: apache-airflow.
What version fixes CVE-2026-33858?
Upgrading to 3.2.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is apache-airflow affected?
Yes, apache-airflow is affected in releases prior to 3.2.0. Upgrade your dependency to 3.2.0 or later.
What is the CVSS score of CVE-2026-33858?
CVE-2026-33858 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-33858?
CVE-2026-33858 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check PyPI dependencies for CVE-2026-33858?
Run the dependency tree command: 'pip show apache-airflow'. 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-mc4f-r875-v87w",
  "modified" : "2026-06-05T14:29:06Z",
  "published" : "2026-04-13T15:31:43Z",
  "aliases" : [ "CVE-2026-33858" ],
  "summary" : "Apache Airflow: Unsafe Deserialization via Legacy Serialization Keys (__type/__var) Bypass in XCom API",
  "details" : "Dag Authors, who normally should not be able to execute code in the webserver context could craft XCom payload causing the webserver to execute arbitrary code. Since Dag Authors are already highly trusted, severity of this issue is Low.\n\n\nUsers are recommended to upgrade to Apache Airflow 3.2.0, which resolves this issue.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "apache-airflow"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "3.1.8"
      }, {
        "fixed" : "3.2.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33858"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apache/airflow/pull/64148"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/apache/airflow"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/apache-airflow/PYSEC-2026-20.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.apache.org/thread/1npt3o2x81s0gw9tmfcv4n7p1z9hdmy0"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2026/04/13/7"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-14T23:17:35Z",
    "nvd_published_at" : "2026-04-13T15:17:33Z"
  }
}