CVE-2026-86485 in YouTrack
Summary
by MITRE • 09/07/2026
In JetBrains YouTrack before 2026.2.18634 iP spoofing via HTTP headers allowed forged Bitbucket webhooks
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Analysis
by VulDB Data Team • 09/07/2026
The vulnerability identified in versions of JetBrains YouTrack prior to build 2026.2.18634 represents a critical security flaw rooted in improper validation of source IP addresses within the application's webhook processing logic. Specifically, the system failed to adequately distinguish between the actual network-level source address and the IP address presented in HTTP headers when handling incoming requests from external services such as Bitbucket. This architectural oversight allows an attacker to manipulate the perceived origin of a request by injecting spoofed values into specific header fields, thereby bypassing security controls that rely on these identifiers for access decisions or trust establishment.
At a technical level, this issue is classified under CWE-294, which describes Improper Authentication via IP Address Spoofing, and aligns with ATT&CK technique T1653, specifically the sub-category of Source Address Spoofing used in phishing or malicious webhook injection scenarios. The flaw exploits the common but often misconfigured practice where web applications prioritize headers like X-Forwarded-For, X-Real-IP, or similar proxies over the actual TCP connection source address without sufficient verification that these headers were set by a trusted intermediary rather than an end-user client. In the context of YouTrack's integration with Bitbucket, this means that if the system trusts header-based IP information for validating webhook signatures or access permissions, an attacker can forge requests that appear to originate from authorized Bitbucket servers while actually being sent from any arbitrary location on the internet.
The operational impact of this vulnerability is significant because it undermines the integrity of automated workflows and integration pipelines. By successfully spoofing the source identity, a malicious actor could inject unauthorized webhook events into YouTrack. This capability allows for the creation of false work items, modification of existing issues without proper authorization, or triggering of automation rules that rely on trusted external inputs. Such manipulation can lead to data integrity loss, disruption of development workflows, and potential escalation privileges if subsequent actions depend on the assumption that incoming webhooks are genuinely from Bitbucket. The trust boundary is effectively blurred, allowing unauthenticated actors to interact with sensitive project management functions under the guise of a legitimate service provider.
Mitigation for this vulnerability requires immediate updates to JetBrains YouTrack version 2026.2.18634 or later, where the developers have corrected the IP validation logic to ensure that source addresses are verified against actual network connections rather than relying solely on potentially spoofable HTTP headers. In environments where upgrading is not immediately feasible, administrators should implement strict firewall rules at the perimeter level to restrict inbound webhook traffic exclusively from known Bitbucket IP ranges, thereby preventing any external host from sending requests regardless of header manipulation. Additionally, enabling mutual TLS authentication or using signed webhooks with secret tokens provides a robust layer of verification that does not depend on network-layer identity assumptions, ensuring that only authenticated and authorized sources can trigger actions within the YouTrack instance.