CVE-2026-44742: Postorius Cross-Site Scripting Vulnerability

HIGH
Advisory Identifier: GHSA-r7c9-7pjq-hmm8
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CVSS 7.2
CWE-79
Published
Advisory Summary

CVE-2026-44742 is a HIGH (CVSS 7.2) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Postorius libraries in the PyPI ecosystem. The issue involves postorius is vulnerable to xss. Remediation is available in the latest vendor maintenance releases.

CVE-2026-44742 at a Glance

CVE Identifier CVE-2026-44742
GHSA Identifier GHSA-r7c9-7pjq-hmm8
Severity HIGH
CVSS v3.1 Base Score 7.2
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Postorius
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.2

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

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-44742

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

postorius fixed: Latest secure release 
pip install postorius>=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 postorius

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-44742, inspect your installed packages using pip:

pip show postorius

Analyze the terminal output to locate any version of Postorius 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 postorius command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Postorius, 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

Postorius through 1.3.13 does not escape HTML in the message subject when rendering it in the Held messages pop-up, as exploited in the wild in May 2026.

CVE-2026-44742 Affected Postorius Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
postorius
pypi/postorius
PyPI
≤ 1.3.13

References

NVD — CVE-2026-44742 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-44742
gitlab.com/mailman/postorius PACKAGE
https://gitlab.com/mailman/postorius
gitlab.com/mailman/postorius/-... WEB
https://gitlab.com/mailman/postorius/-/commit/c4706abd05ba6bcf472fc674b160d3a9d6a4868b
gitlab.com/mailman/postorius/-... WEB
https://gitlab.com/mailman/postorius/-/issues/620
gitlab.com/mailman/postorius/-... WEB
https://gitlab.com/mailman/postorius/-/merge_requests/972
Postorius Security Information SECURITY
https://www.openwall.com/lists/oss-security/2026/05/07/3

Frequently Asked Questions

What is CVE-2026-44742?
CVE-2026-44742 is a security vulnerability in Postorius involving Postorius is vulnerable to XSS under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Postorius versions are affected?
Affected versions include releases prior to current release patches across affected packages: postorius.
What version fixes CVE-2026-44742?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is postorius affected?
Yes, postorius 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-2026-44742?
CVE-2026-44742 has a CVSS v3.1 base score of 7.2 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-44742?
CVE-2026-44742 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check PyPI dependencies for CVE-2026-44742?
Run the dependency tree command: 'pip show postorius'. 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-r7c9-7pjq-hmm8",
  "modified" : "2026-05-12T16:20:35Z",
  "published" : "2026-05-07T21:30:29Z",
  "aliases" : [ "CVE-2026-44742" ],
  "summary" : "Postorius is vulnerable to XSS",
  "details" : "Postorius through 1.3.13 does not escape HTML in the message subject when rendering it in the Held messages pop-up, as exploited in the wild in May 2026.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "postorius"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.3.13"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44742"
  }, {
    "type" : "PACKAGE",
    "url" : "https://gitlab.com/mailman/postorius"
  }, {
    "type" : "WEB",
    "url" : "https://gitlab.com/mailman/postorius/-/commit/c4706abd05ba6bcf472fc674b160d3a9d6a4868b"
  }, {
    "type" : "WEB",
    "url" : "https://gitlab.com/mailman/postorius/-/issues/620"
  }, {
    "type" : "WEB",
    "url" : "https://gitlab.com/mailman/postorius/-/merge_requests/972"
  }, {
    "type" : "WEB",
    "url" : "https://www.openwall.com/lists/oss-security/2026/05/07/3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-12T16:20:35Z",
    "nvd_published_at" : "2026-05-07T19:16:02Z"
  }
}