CVE-2026-41426: Pretalx Pretalx Mail Templates Vulnerable To Vulnerability

MODERATE
Advisory Identifier: GHSA-jm8c-9f3j-4378
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CVSS 6.1
CWE-116 CWE-79
Published
Advisory Summary

CVE-2026-41426 is a MODERATE (CVSS 6.1) pretalx mail templates vulnerable to vulnerability (CWE-116: Improper Encoding or Escaping of Output) affecting Pretalx libraries in the PyPI ecosystem. The issue involves pretalx mail templates vulnerable to email injection via unescaped user-controlled placeholders. Remediation is available by upgrading affected packages to version 2026.1.0.

CVE-2026-41426 at a Glance

CVE Identifier CVE-2026-41426
GHSA Identifier GHSA-jm8c-9f3j-4378
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-116: Improper Encoding or Escaping of Output
Affected Product Pretalx
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.1

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:R/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 Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-41426

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

pretalx fixed: 2026.1.0 
pip install pretalx>=2026.1.0
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 pretalx

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-41426, inspect your installed packages using pip:

pip show pretalx

Analyze the terminal output to locate any version of Pretalx in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2026.1.0), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-116: Improper Encoding or Escaping of Output, where the product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. as a result, the intended structure of the message is not preserved. In Pretalx, 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

An unauthenticated attacker can send arbitrary HTML-rendered emails from a pretalx instance's configured sender address by embedding malformed HTML or markdown link syntax in a user-controlled template placeholder such as the account display name. The most direct vector is the password-reset flow: the attacker registers an account with a malicious name, enters the victim's email address, and triggers a password reset. The resulting email is delivered from the event's legitimate sender address and passes SPF/DKIM/DMARC validation, making it a ready-made phishing vector. The same class of bug affects every mail template that interpolates a user-controlled placeholder (speaker name, proposal title, biography, question answers, etc.), including organiser-triggered emails such as acceptance/rejection notifications. ### Credits Thanks go to Mark Fijneman for finding and reporting a subset of this issue, which alerted us to the wider vulnerability.

CVE-2026-41426 Affected Pretalx Versions

1 component(s)
Fixed Versions:
2026.1.0
Product / Package Ecosystem Affected Versions Fixed Version
pretalx
pypi/pretalx
PyPI
< 2026.1.0
2026.1.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/pretalx/pretalx/security/advisories/GHSA-jm8c-9f3j-4378
NVD — CVE-2026-41426 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-41426
Pretalx Source Repository REPOSITORY
https://github.com/pretalx/pretalx
Pretalx Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/pretalx/PYSEC-2026-109.yaml

Frequently Asked Questions

What is CVE-2026-41426?
CVE-2026-41426 is a security vulnerability in Pretalx involving pretalx mail templates vulnerable to email injection via unescaped user-controlled placeholders under CWE-116: Improper Encoding or Escaping of Output.
Which Pretalx versions are affected?
Affected versions include releases prior to 2026.1.0 across affected packages: pretalx.
What version fixes CVE-2026-41426?
Upgrading to 2026.1.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pretalx affected?
Yes, pretalx is affected in releases prior to 2026.1.0. Upgrade your dependency to 2026.1.0 or later.
What is the CVSS score of CVE-2026-41426?
CVE-2026-41426 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-41426?
CVE-2026-41426 is classified under CWE-116: Improper Encoding or Escaping of Output (The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.).
How can I check PyPI dependencies for CVE-2026-41426?
Run the dependency tree command: 'pip show pretalx'. 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-jm8c-9f3j-4378",
  "modified" : "2026-06-08T19:03:12Z",
  "published" : "2026-04-18T01:11:19Z",
  "aliases" : [ "CVE-2026-41426" ],
  "summary" : "pretalx mail templates vulnerable to email injection via unescaped user-controlled placeholders",
  "details" : "An unauthenticated attacker can send arbitrary HTML-rendered emails from a pretalx instance's configured sender address by embedding malformed HTML or markdown link syntax in a user-controlled template placeholder such as the account display name. The most direct vector is the password-reset flow: the attacker registers an account with a malicious name, enters the victim's email address, and triggers a password reset. The resulting email is delivered from the event's legitimate sender address and passes SPF/DKIM/DMARC validation, making it a ready-made phishing vector.\n\nThe same class of bug affects every mail template that interpolates a user-controlled placeholder (speaker name, proposal title, biography, question answers, etc.), including organiser-triggered emails such as acceptance/rejection notifications.\n\n### Credits\n\nThanks go to Mark Fijneman for finding and reporting a subset of this issue, which alerted us to the wider vulnerability.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pretalx"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2026.1.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pretalx/pretalx/security/advisories/GHSA-jm8c-9f3j-4378"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-41426"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pretalx/pretalx"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/pretalx/PYSEC-2026-109.yaml"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-116", "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-18T01:11:19Z",
    "nvd_published_at" : "2026-04-24T20:16:27Z"
  }
}