Compliance Impact

The CVE-2026-39845 vulnerability involves a Server-Side Request Forgery (SSRF) issue in Weblate's webhook add-on that could allow an attacker with high privileges to make unauthorized requests, potentially exposing sensitive data.

Such unauthorized data exposure risks could impact compliance with data protection regulations like GDPR and HIPAA, which require safeguarding confidentiality and preventing unauthorized access to sensitive information.

However, the vulnerability has a low confidentiality impact and no integrity or availability impact, and it requires high privileges to exploit, which somewhat limits the risk.

The fix implemented in version 5.17 enforces strict outbound URL validation to block private network targets, mitigating the SSRF risk and improving security posture, thereby helping maintain compliance with relevant security standards.

Until the update is applied, disabling the webhook add-on is recommended as a workaround to prevent potential misuse.

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Executive Summary

CVE-2026-39845 is a Server-Side Request Forgery (SSRF) vulnerability in the Weblate web-based localization tool, specifically affecting the webhook add-on in versions prior to 5.17.

The vulnerability arises because the webhook add-on used an unprotected function to send outbound HTTP requests, which did not apply existing SSRF protections. This allowed attackers with high privileges to make the server send unauthorized requests to unintended or internal network destinations.

The issue was fixed in version 5.17 by changing the webhook delivery mechanism to use a validated URL fetching function that blocks requests to private network addresses unless explicitly allowed, thereby mitigating SSRF risks.

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Impact Analysis

This vulnerability can allow an attacker with high privileges to exploit the webhook add-on to make the Weblate server send unauthorized requests to internal or unintended network destinations.

Such exploitation can lead to exposure of sensitive internal network information, potentially impacting confidentiality.

The CVSS score indicates a moderate severity with low confidentiality impact, no integrity or availability impact, but the scope of the vulnerability is changed, meaning it affects components beyond its original security boundary.

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Detection Guidance

Detection of this vulnerability involves monitoring webhook delivery attempts that target private network addresses, which are blocked and logged by the updated Weblate webhook add-on.

Since the vulnerability involves Server-Side Request Forgery (SSRF) via webhook URLs, you can check Weblate logs for errors related to blocked webhook requests to private IP ranges.

Commands to detect potential exploitation attempts could include searching Weblate log files for error messages indicating blocked webhook deliveries to private networks. For example:

• grep -i 'webhook' /var/log/weblate/weblate.log | grep -i 'blocked'
• grep -E '10\.|192\.168\.|172\.(1[6-9]|2[0-9]|3[0-1])\.' /var/log/weblate/weblate.log

Additionally, network monitoring tools can be used to detect unusual outbound HTTP requests from the Weblate server to internal IP addresses.

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Mitigation Strategies

The primary mitigation is to upgrade Weblate to version 5.17 or later, where the webhook add-on uses validated URL fetching that blocks SSRF attempts targeting private networks.

If immediate upgrade is not possible, the recommended workaround is to disable the webhook add-on entirely to prevent exploitation.

Additionally, review and configure the webhook settings to restrict private network targets by ensuring the default setting `allow_private_targets=False` is enforced.

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