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CVE-2019-14870

MEDIUMCVSS 5.4/10EPSS 2.78%

Last modified

CVE-2019-14870 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable. In AD this is implemented by a user attribute delegation_not_allowed (aka not-delegated), which translates to disallow-forwardable. EPSS estimates a 2.78% chance of exploitation in the next 30 days.

Description

All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable. In AD this is implemented by a user attribute delegation_not_allowed (aka not-delegated), which translates to disallow-forwardable. However the Samba AD DC does not do that for S4U2Self and does set the forwardable flag even if the impersonated client has the not-delegated flag set.

Metrics

CVSS 3.1
5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

EPSS Probability
2.78%

84.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
SambaSamba>= 4.0.0, < 4.9.17
SambaSamba>= 4.10.0, < 4.10.11
SambaSamba>= 4.11.0, < 4.11.3
FedoraprojectFedora30
FedoraprojectFedora31
CanonicalUbuntu Linux14.04
CanonicalUbuntu Linux16.04
CanonicalUbuntu Linux18.04
CanonicalUbuntu Linux19.04
CanonicalUbuntu Linux19.10
DebianDebian Linux9.0
DebianDebian Linux10.0
OpensuseLeap15.1

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2019-14870?
All Samba versions 4.x.x before 4.9.17, 4.10.x before 4.10.11 and 4.11.x before 4.11.3 have an issue, where the S4U (MS-SFU) Kerberos delegation model includes a feature allowing for a subset of clients to be opted out of constrained delegation in any way, either S4U2Self or regular Kerberos authentication, by forcing all tickets for these clients to be non-forwardable. In AD this is implemented by a user attribute delegation_not_allowed (aka not-delegated), which translates to disallow-forwardable. However the Samba AD DC does not do that for S4U2Self and does set the forwardable flag even if the impersonated client has the not-delegated flag set.
How severe is CVE-2019-14870?
CVE-2019-14870 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 2.78% probability of exploitation in the next 30 days.
How do I fix CVE-2019-14870?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2019-14870?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST