A critical vulnerability in open source automation tool Jenkins could allow permission checks to be bypassed through the use of specially-crafted URLs . Jenkins uses the Stapler web framework for HTTP request handling , which uses reflection to dispatch incoming web requests to controller code . This means that any public methods that start with get and include string and integer parameters are exposed to the web server . Because this is a common naming convention , this has led to multiple internal Jenkins methods being inadvertently exposed . The precise impact of this isn ’ t clear . The advisory notes that code execution could be a possible outcome – though on closer inspection , this seems to be a worst-case scenario . “ To clarify , the vulnerability we addressed Vulnerability-related.PatchVulnerability had nothing to do with arbitrary code execution , but was rather an issue discovered Vulnerability-related.DiscoverVulnerability by the Jenkins security team that allowed a small subset of existing Jenkins code to be invoked by a remote client , ” Daniel Beck , Jenkins security officer , told The Daily Swig in an email . “ While the known impact is pretty limited , we felt that the layer at which the vulnerability existed , and its potential warranted a higher score. ” These potential attacks include unauthenticated users being able to invalidate sessions when running with the built-in server , and users with overall/read permissions being able to create new user objects in memory . The advisory reads : “ Given the vast potential attack surface , we fully expect other attacks , that we are not currently aware of , to be possible on Jenkins releases that do not have this fix applied Vulnerability-related.PatchVulnerability . “ This is reflected in the high score we assigned Vulnerability-related.DiscoverVulnerability to this issue , rather than limiting the score to the impact through known issues. ” Beck added : “ Jenkins users should always keep their instances up to date . In this case , we released Vulnerability-related.PatchVulnerability updates for two LTS lines simultaneously for the first time , so admins could apply Vulnerability-related.PatchVulnerability the update without having to go through a major version jump . “ We strive to fix Vulnerability-related.PatchVulnerability all security vulnerabilities in Jenkins and plugins in a timely manner. ” Reflection is also used by Apache Struts , via the OGNL library . Struts has suffered Vulnerability-related.DiscoverVulnerability a number of serious security flaws in recent years . In 2017 , a vulnerability in the framework was exploited Vulnerability-related.DiscoverVulnerability to expose Attack.Databreach the details of up to 148 million Equifax customers . Another flaw , revealed Vulnerability-related.DiscoverVulnerability in August 2018 , could lead to remote code execution . These issues underline the dangers of using reflection with untrusted data , and application architects would do well to avoid this unsafe practice .