CVE-2021-21687

Jenkins 2.318 and earlier, LTS 2.303.2 and earlier does not check agent-to-controller access to create symbolic links when unarchiving a symbolic link in FilePath#untar.

Published: 2021-11-04 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-21687 is rated Moderate Risk (61.1/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 1.34%). EPSS rose +1.07% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-21687

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.27% 1.34% +1.07%
2 2026-03-04 0.23% 0.27% +0.04%
3 2026-03-01 — 0.23% —

Full EPSS history (38 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-21687

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.1 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 5.2 [email protected]
6.4 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 4.9 [email protected]

Weakness enumeration for CVE-2021-21687

GitHub Security Advisory for CVE-2021-21687

GHSA-3q84-vrvx-rfvf · Severity: critical · Ecosystem: maven — Multiple vulnerabilities allow bypassing path filtering of agent-to-controller access control in Jenkins

OS Trackers for CVE-2021-21687

vendor priority summary link
alpine critical CVE-2021-21687: 1 source package rows (jenkins); 8 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 8. https://security.alpinelinux.org/vuln/CVE-2021-21687
redhat high — https://access.redhat.com/security/cve/CVE-2021-21687

Affected software / configurations for CVE-2021-21687

Vendor Product Version Raw CPE
jenkins jenkins < 2.303.3 cpe:2.3:a:jenkins:jenkins:*:*:*:*:lts:*:*:*
jenkins jenkins < 2.319 cpe:2.3:a:jenkins:jenkins:*:*:*:*:-:*:*:*

References for CVE-2021-21687

cvelogic Threat Intelligence