Jenkins CVE-2026-53441

The attacker must hold Agent/Configure permission within the Jenkins instance - this is a non-default, explicitly granted role required for agent management. The target victim (who triggers the XSS payload) must navigate to a Jenkins page that renders the compromised agent's offline cause description (UI:R); a passive attacker cannot force this without social engineering or timing an agent offline event to attract administrator attention. The vulnerable endpoint is the POST config.xml API, which must be network-reachable by the attacker (AV:N). Exploitation is limited to Jenkins versions 2.483-2.567 (weekly) and 2.492.1-2.555.2 (LTS); there is no special non-default configuration required beyond the attacker holding Agent/Configure permission. There is no availability impact and no unauthenticated exploitation path.

The NVD-assigned CVSS 3.1 score of 5.4 Medium (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N) accurately models the attack surface: network-reachable, low complexity, but gated behind Agent/Configure permission (PR:L) and requiring a victim to load the affected page (UI:R). These two limiting factors significantly reduce real-world impact compared to higher-severity XSS flaws. EPSS at 0.02% (5th percentile) is consistent with the access-control barrier and absence of known POC. No CISA KEV listing is present. The S:C metric is the most impactful signal here - successful exploitation crosses user-session boundaries and could allow an attacker to compromise a Jenkins administrator's session, escalating from a low-privilege agent configurator to effective administrator control. This makes the vulnerability higher priority in multi-tenant Jenkins environments or those with many users holding Agent/Configure permission. In single-admin or tightly access-controlled deployments, real-world risk is low. No conflicting signals are present in the available data.

An attacker granted Agent/Configure permission authenticates to Jenkins and issues a POST config.xml request to a target agent, embedding a JavaScript payload in the generic offline cause description field. The payload is stored in the Jenkins configuration. When a Jenkins administrator later views the agent status or configuration page - for example, while diagnosing why the agent went offline - the unescaped script executes in their browser, exfiltrating their session cookie to an attacker-controlled endpoint and granting the attacker administrative access to the Jenkins instance.