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Not in CISA KEV
MEDIUM severity

CVE-2026-41426 — pretalx

MEDIUM

CVE-2026-41426 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in pretalx. A fix is available for pretalx — see the affected versions and patch details below.

pretalx: Email injection via unescaped user-controlled placeholders in pretalx mail templates

Also known asGHSA-jm8c-9f3j-4378PYSEC-2026-109
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-41426.

EPSS Exploitation Probability

via FIRST.org ↗
0.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs5th percentile — riskier than 5% of all scored CVEsHighest risk
0.00%0.25%0.51%0.76%0.0%0.2%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍pretalx

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIpretalxall versions2026.1.0pip install --upgrade 'pretalx==2026.1.0'

Affected Products

1 product · 1 configurations
Application
pretalxpretalx
< 2026.1.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pretalx, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update pretalx to 2026.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41426 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

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 a
O3 Security · Impact-Aware SCA

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CVE-2026-41426: pretalx — Fixed in 2026.1.0