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Jenkins EUVDEUVD-2026-112186

| CVE-2026-117621 CRITICAL
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Gain control of a build agent process
  2. Delivery
    Return crafted file/directory names
  3. Exploit
    Agent computes malicious link URL
  4. Execution
    Victim opens controller workspace browser
  5. Impact
    Script executes in victim's session

Vulnerability Assessment

Exploitation Conditions

Exploitation requires the attacker to be in control of an agent process (a malicious or compromised build agent) whose workspace is browsed via the controller's workspace browser, and requires a controller user to actually open that workspace browser view for the resulting stored XSS to fire. It applies only when a job's workspace is located on an agent (not on the controller itself). Limiting factors: the attacker must already hold agent control rather than mere anonymous or low-privilege web access; victim interaction (viewing the workspace browser) is needed; and on Jenkins 2.539+/LTS 2.541.1+ with Content Security Policy protection enforced, the vendor states the known impact is mitigated. Affected: Jenkins 2.587 and earlier, LTS 2.580.1 and earlier; fixed in 2.588 and LTS 2.580.2.

Impact

No CVSS vector is provided in any source (the Jenkins advisory and NVD-style fields both show CVSS/CWE as N/A), so severity cannot be anchored to attack-vector/complexity/privilege metrics from the input - the Jenkins advisory itself rates the parent batch items only as qualitative 'High' for other CVEs and gives no rating excerpt for SECURITY-4232. There is no EPSS score, no CISA KEV listing, and no PoC or exploit reference in the provided data; the vuln.today Decision label is 'awaiting_data', which explicitly signals that priority-scoring inputs are incomplete rather than that the issue is urgent. The defining constraint is the prerequisite stated in the description: exploitation requires an attacker who is already 'in control of agent processes' - i.e., a compromised or attacker-operated build agent - which is a meaningfully privileged starting position, not anonymous network access. The impact is a stored cross-site scripting vulnerability in the controller's workspace browser (the agent computes the per-file link URL), so the realistic consequence is script execution in the browser session of a controller user who views that workspace, not direct controller RCE. Net assessment: this is a lower-tier, conditional issue within a larger multi-CVE Jenkins advisory - real and worth patching, but gated behind agent control and further mitigated by Content Security Policy on supported versions; absent CVSS, EPSS, KEV, and PoC data, treat the raw severity as unconfirmed and prioritize the RCE-class items in the same advisory (e.g., CVE-2026-117612/117614) ahead of it.

Exploit ScenarioDerived

An attacker who controls a build agent (a rogue agent, or one compromised via another flaw) causes that agent to return file or directory entries whose names/URLs embed a malicious script payload. When a legitimate Jenkins user opens the workspace browser for that agent-hosted job on the controller, the attacker-computed link is rendered and the script executes in the victim's authenticated session. No public exploit code or PoC reference is present in the provided data.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
No patch listed yet

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AnalysisAIv1 – Oct 28, 2026

Cross-site scripting in the Jenkins workspace browser lets an attacker who controls a build agent have script execute in the browser of a Jenkins user who opens the workspace listing for that agent. Only jobs whose workspace resides on an agent are affected, specifically Jenkins 2.587 and earlier and Jenkins LTS 2.580.1 and earlier, and the attacker must already control the agent process while a victim must actually view the workspace browser (assessed CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N). The Jenkins advisory publishes no CVSS score or CWE for this item, there is no CISA KEV listing, no public exploit identified at time of analysis, and no EPSS data in the supplied sources.

RemediationAI

Vendor-released patch: upgrade to Jenkins 2.588 or Jenkins LTS 2.580.2, the releases named in the advisory as containing the fixes for the whole 2026-10-28 batch, including SECURITY-4232. For deployments that cannot upgrade immediately, the vendor's stated interim control is to enforce Content Security Policy protection, which mitigates the known impact of this XSS on Jenkins 2.539 and newer / LTS 2.541.1 and newer; CSP enforcement in Jenkins can interfere with plugins and UI features that rely on inline resources, so test before rolling it out broadly. Because the flaw only fires when a user opens the workspace browser for a workspace hosted on an attacker-influenced agent, avoiding that view for agents that are not fully trusted removes the trigger at the cost of losing the workspace file browser for those jobs. Confirm the running version from the Jenkins UI or via the CLI before and after upgrading, and treat any agent that may have been compromised as a potential source of injected link data when reviewing logs. The full advisory and version guidance are at https://www.jenkins.io/security/advisory/2026-10-28/, with reporting guidance at https://www.jenkins.io/security/#reporting-vulnerabilities.

Affected VersionsENISA

Jenkins patch: 2.588
Jenkins patch: 2.580.2

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Technical ContextAI · show details

Jenkins serves configuration and build data through XStream-based serialization, but this item (SECURITY-4232 / CVE-2026-117621) is a UI-layer trust-boundary bug rather than a deserialization flaw. When a job's workspace lives on an agent, the controller asks that agent for the list of files and directories to display in the workspace browser, and in Jenkins 2.587 and earlier / LTS 2.580.1 and earlier the agent - not the controller - computes the URL used for each file and directory link. Because that agent-supplied link value is rendered in the controller's web UI without adequate validation, an attacker in control of an agent process can craft entries that break out of the link context and execute script in the session of a user browsing that workspace, which is why the impact is scoped to confidentiality and integrity (C:L/I:L) with scope change. Exploitation is conditional: it applies only when the workspace is located on an agent rather than the controller, requires the attacker to already hold agent control (PR:H), and requires the victim to open the workspace browser view (UI:R). The advisory gives no CVSS score or CWE for this specific entry (both N/A in the supplied data); the vendor's TIP notes that on Jenkins 2.539 and newer / LTS 2.541.1 and newer, enforcing Content Security Policy protection mitigates the known impact of this XSS, and that other XSS or related element-type issues may also be possible in the same class of bug.

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Severity by source

vuln.today AI 4.8 MEDIUM

Stored XSS requires control of an agent process (PR:H) and a user viewing the workspace browser (UI:R); payload executes in a different security context (S:C) with limited C/I impact and no availability impact.

3.1 AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:N/PR:H/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Description PRE-NVD

Disclosed via oss-security. NVD scoring and full description are pending.

Executive ViewAI

Why It Matters

A critical cross-site scripting vulnerability in Jenkins workspace browser (CVE-2026-117621) could allow an attacker who already controls a build agent to execute malicious scripts in the browser of Jenkins users viewing that agent's workspace. This affects Jenkins 2.587 and earlier and LTS 2.580.1 and earlier, compromising the integrity and confidentiality of build data for organizations using these versions. While exploitation requires the attacker to first compromise an agent, the potential for lateral movement and data theft makes this a priority for security leadership.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: restrict access to the Jenkins workspace browser to trusted users, isolate build agents from sensitive networks, monitor agent processes for unauthorized changes, and consider disabling the workspace browser feature if feasible.

Threat Intelligence Overview

Prevalence
High
Jenkins is a widely deployed enterprise CI/CD automation server
Data Quality
2 sources
Confidence: Low

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity CRITICAL
CISA KEV No
Public POC No
EPSS N/A
Patch available No
Active threat No
Deciding rule
CRITICAL severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

Attack Technique

Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.

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