01 Record

CVE-2026-40356

In MIT Kerberos 5 (aka krb5) before 1.22.3, there is an integer underflow and resultant out-of-bounds read if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism

MediumPUBLISHEDCNA: mitre

CNA base score5.9 CVSS v3.xCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

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02 Description

In MIT Kerberos 5 (aka krb5) before 1.22.3, there is an integer underflow and resultant out-of-bounds read if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism

03 Exploitation and scoring

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.60% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 48.5% of scored records. A rank, not a probability.

NVD base score

7.5 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Analyzed. NVD last modified this record on 2026-10-26.

Red Hat severity

Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published

2026-04-28 00:00Z6 MO AGO

Last updated

2026-04-28 13:10Z6 MO AGO

Reserved

2026-04-11

Assigning CNA

mitre

Record state

PUBLISHED

Severity

Medium (CVSS 5.9)

CNA CVSS vector

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

Weaknesses

CWE-191Integer Underflow (Wrap or Wraparound)Base

Data version

5.2

Document digest

d53cba1bdc9a7bf99f7551ed4850830957b66fe90f628ff1d44d971686cbc45e

05 Affected products

VendorProductVersionsPlatforms

MITKerberos 51.18 to < 1.22.3—

06 References

07 Fixed in

AlmaLinux 8

krb5-devel
Fixed in 1.18.2-34.el8_10
krb5-libs
Fixed in 1.18.2-34.el8_10
krb5-pkinit
Fixed in 1.18.2-34.el8_10
krb5-server
Fixed in 1.18.2-34.el8_10
krb5-server-ldap
Fixed in 1.18.2-34.el8_10
krb5-workstation
Fixed in 1.18.2-34.el8_10
libkadm5
Fixed in 1.18.2-34.el8_10

AlmaLinux 9

krb5-devel
Fixed in 1.21.1-10.el9_8
krb5-libs
Fixed in 1.21.1-10.el9_8
krb5-pkinit
Fixed in 1.21.1-10.el9_8
krb5-server
Fixed in 1.21.1-10.el9_8
krb5-server-ldap
Fixed in 1.21.1-10.el9_8
krb5-workstation
Fixed in 1.21.1-10.el9_8
krb5-xrealmauthz
Fixed in 1.21.1-10.el9_8
libkadm5
Fixed in 1.21.1-10.el9_8

AlmaLinux 10

krb5-devel
Fixed in 1.21.3-10.el10_2
krb5-libs
Fixed in 1.21.3-10.el10_2
krb5-pkinit
Fixed in 1.21.3-10.el10_2
krb5-server
Fixed in 1.21.3-10.el10_2
krb5-server-ldap
Fixed in 1.21.3-10.el10_2
krb5-workstation
Fixed in 1.21.3-10.el10_2
krb5-xrealmauthz
Fixed in 1.21.3-10.el10_2
libkadm5
Fixed in 1.21.3-10.el10_2

CloudLinux 8

krb5-devel
Fixed in 1.18.2-34.el8_10
krb5-libs
Fixed in 1.18.2-34.el8_10
krb5-pkinit
Fixed in 1.18.2-34.el8_10
krb5-server
Fixed in 1.18.2-34.el8_10
krb5-server-ldap
Fixed in 1.18.2-34.el8_10
krb5-workstation
Fixed in 1.18.2-34.el8_10
libkadm5
Fixed in 1.18.2-34.el8_10

Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.

CloudLinux 9

krb5-devel
Fixed in 1.21.1-10.el9_8
krb5-libs
Fixed in 1.21.1-10.el9_8
krb5-pkinit
Fixed in 1.21.1-10.el9_8
krb5-server
Fixed in 1.21.1-10.el9_8
krb5-server-ldap
Fixed in 1.21.1-10.el9_8
krb5-workstation
Fixed in 1.21.1-10.el9_8
krb5-xrealmauthz
Fixed in 1.21.1-10.el9_8
libkadm5
Fixed in 1.21.1-10.el9_8

Derived from AlmaLinux 9. Partial coverage: only packages taken from AlmaLinux 9 are listed.

CloudLinux 10

krb5-devel
Fixed in 1.21.3-10.el10_2
krb5-libs
Fixed in 1.21.3-10.el10_2
krb5-pkinit
Fixed in 1.21.3-10.el10_2
krb5-server
Fixed in 1.21.3-10.el10_2
krb5-server-ldap
Fixed in 1.21.3-10.el10_2
krb5-workstation
Fixed in 1.21.3-10.el10_2
krb5-xrealmauthz
Fixed in 1.21.3-10.el10_2
libkadm5
Fixed in 1.21.3-10.el10_2

Derived from AlmaLinux 10. Partial coverage: only packages taken from AlmaLinux 10 are listed.

Debian 12

krb5
Fixed in 1.20.1-2+deb12u5

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

krb5
Fixed in 1.21.3-5+deb13u1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

krb5
Fixed in 1.22.1-2.1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 22.04 LTS

krb5
Fixed in 1.19.2-2ubuntu0.8

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 24.04 LTS

krb5
Fixed in 1.20.1-6ubuntu2.7

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 25.10

krb5
No fix yet

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 26.04 LTS

krb5
Fixed in 1.22.1-2ubuntu4.1

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.