Jenkins 2.275 and LTS 2.263.2 allows reading arbitrary files using the file browser for workspaces and archived artifacts due to a time-of-check to time-of-use (TOCTOU) race condition.
http://www.openwall.com/lists/oss-security/2021/01/26/2
https://www.jenkins.io/security/advisory/2021-01-26/#SECURITY-2197
Source: MITRE
Published: 2021-01-26
Updated: 2021-02-02
Type: CWE-367
Base Score: 3.5
Vector: AV:N/AC:M/Au:S/C:P/I:N/A:N
Impact Score: 2.9
Exploitability Score: 6.8
Severity: LOW
Base Score: 5.3
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Impact Score: 3.6
Exploitability Score: 1.6
Severity: MEDIUM