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CVE-2021-21671

Session fixation vulnerability in Jenkins

7.5 HighFix available

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier does not invalidate the previous session on login.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

1.75%Up 1.1 points since Jul 1, 2021
90%50%10%1%

What each source reports

NVD Score used 7.5

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier does not invalidate the previous session on login.

Record
CVE-2021-21671
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS 2.0
5.1 MediumAV:N/AC:H/Au:N/C:P/I:P/A:P
Updated
2026-11-02
CVE List No score

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier does not invalidate the previous session on login.

Record
CVE-2021-21671
Updated
2026-11-02
EUVDEUVD-2022-2462 No score

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier does not invalidate the previous session on login.

Record
EUVD-2022-2462
Updated
2026-11-03
GitHub AdvisoriesGHSA-4wr9-2xc6-jmg5 7.5

Session fixation vulnerability in Jenkins

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier does not invalidate the previous session on login. This allows attackers to use social engineering techniques to gain administrator access to Jenkins.

This vulnerability was introduced in Jenkins 2.266 and LTS 2.277.1.

Jenkins 2.300, LTS 2.289.2 invalidates the previous session on login.

In case of problems, administrators can choose a different implementation by setting the Java system property hudson.security.SecurityRealm.sessionFixationProtectionMode to 2, or disable the fix entirely by setting that system property to 0.

Record
GHSA-4wr9-2xc6-jmg5
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-384
Updated
2026-11-02
OSV 7.5

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier does not invalidate the previous session on login.

Record
CVE-2021-21671
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVGHSA-4wr9-2xc6-jmg5 7.5

Session fixation vulnerability in Jenkins

Jenkins 2.299 and earlier, LTS 2.289.1 and earlier does not invalidate the previous session on login. This allows attackers to use social engineering techniques to gain administrator access to Jenkins.

This vulnerability was introduced in Jenkins 2.266 and LTS 2.277.1.

Jenkins 2.300, LTS 2.289.2 invalidates the previous session on login.

In case of problems, administrators can choose a different implementation by setting the Java system property hudson.security.SecurityRealm.sessionFixationProtectionMode to 2, or disable the fix entirely by setting that system property to 0.

Record
GHSA-4wr9-2xc6-jmg5
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-384
Updated
2026-11-02
Show 4 moreShow less
OSVRHBA-2021:3033 7.5

Red Hat Bug Fix Advisory: OpenShift Container Platform 4.7.24 packages update

Record
RHBA-2021:3033
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVRHBA-2021:3396 7.5

Red Hat Bug Fix Advisory: OpenShift Container Platform 4.6.44 packages update

Record
RHBA-2021:3396
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVRHSA-2021:3820 7.5

Red Hat Security Advisory: OpenShift Container Platform 4.8.15 packages and security update

Record
RHSA-2021:3820
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVBIT-jenkins-2021-21671 No score

Jenkins LTS 2.289.1 and earlier does not invalidate the previous session on login.

Record
BIT-jenkins-2021-21671
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
org.jenkins-ci.main:jenkins-core
Maven
 2.292 to 2.299
2.300
org.jenkins-ci.main:jenkins-core
Maven
 through 2.289.1
2.289.2
jenkins
Bitnami
 2.266.0 up to 2.300.0
2.300.0
org.jenkins-ci.main:jenkins-core
Maven
 2.292 up to 2.300, plus listed versions
2.2932.2942.2952.2962.2972.2982.299
2.300
org.jenkins-ci.main:jenkins-core
Maven
 before 2.289.2, plus listed versions
1.3961.3971.3981.3991.400
Show 45 moreShow less
1.4011.4031.4041.4051.4061.4071.4081.4091.409.11.409.21.409.31.4101.4111.4121.4131.4141.4151.4161.4171.4181.4191.4201.4211.4221.4231.4241.424.11.424.21.424.31.424.41.424.51.424.61.4251.4261.4271.4281.4291.4301.4311.4321.4331.4341.4351.4361.437
2.289.2
jenkins
Red Hat:openshift:4.7::el8
From an advisory covering 2 CVEs
 before 0:2.289.2.1628252553-1.el8
0:2.289.2.1628252553-1.el8
jenkins
Red Hat:openshift:4.6::el8
From an advisory covering 2 CVEs
 before 0:2.289.2.1629437819-1.el8
0:2.289.2.1629437819-1.el8
jenkins
Red Hat:openshift:4.8::el8
From an advisory covering 6 CVEs
 before 0:2.289.3.1633554819-1.el8
0:2.289.3.1633554819-1.el8
butane
Red Hat:openshift:4.8::el8
From an advisory covering 6 CVEs
 before 0:0.12.1-2.rhaos4.8.el8
0:0.12.1-2.rhaos4.8.el8
butane-debuginfo
Red Hat:openshift:4.8::el8
From an advisory covering 6 CVEs
 before 0:0.12.1-2.rhaos4.8.el8
0:0.12.1-2.rhaos4.8.el8

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-21671 is a high vulnerability (CVSS 7.5) in Jenkins, published June 30, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.75%, the 78th percentile. Fixed in org.jenkins-ci.main:jenkins-core 2.300.

References

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