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CVE-2026-40355

36
FAUCET Score

In MIT Kerberos 5 (aka krb5) before 1.22.3, there is a NULL pointer dereference if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, causing the process to terminate in parse_nego_message.

First published: Apr 28, 2026Last modified: Apr 28, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.18.0, <= 1.22.2CPE matchmatch criteria
cpe:2.3:a:mit:kerberos_5:*:*:*:*:*:*:*:*
>= 1.18, < 1.22.3CPE match
cpe:2.3:a:mit:kerberos_5:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.9MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.61%
Probability of exploitation in next 30 days
EPSS Percentile
45.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0061 is in the 22nd percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (15)

github_advisorypatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: 21405-17084Fixed in: 1.21.3-4
microsoftpatch availablevia msrc
Product: 20902-17084Fixed in: 1.21.3-4
microsoftpatch availablevia msrc
Product: azl3 krb5 1.21.3-3 on Azure Linux 3.0Fixed in: 1.21.3-4
microsoftpatch availablevia msrc
Product: azl3 krb5 1.21.3-4 on Azure Linux 3.0Fixed in: 1.21.3-4
ubuntupatch availablevia ubuntu_usn
Product: krb5 (jammy)Fixed in: 1.19.2-2ubuntu0.8
ubuntupatch availablevia ubuntu_usn
Product: krb5 (noble)Fixed in: 1.20.1-6ubuntu2.7
ubuntupatch availablevia ubuntu_usn
Product: krb5 (resolute)Fixed in: 1.22.1-2ubuntu4.1
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: krb5
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: krb5
redhatvendor investigatingvia redhat_api
Product: Red Hat Hardened ImagesFixed in: krb5
redhatvendor investigatingvia redhat_api
Product: Red Hat OpenShift Container Platform 4Fixed in: rhcos
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: krb5
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: krb5
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: krb5

Vendor Advisories (3)

ubuntuUSN-8585-1

Kerberos vulnerabilities

Jul 22, 2026
redhatCVE-2026-40355Moderate

krb5: MIT Kerberos 5: Denial of Service via NULL pointer dereference in NegoEx mechanism

Apr 28, 2026
microsoft2026-Apr/CVE-2026-40355Moderate

In MIT Kerberos 5 (aka krb5) before 1.22.3, there is a NULL pointer dereference if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, causing the process to terminate in parse_nego_message.

Apr 14, 2026

References

cert-portal.siemens.com / productcert/html/ssa-019113.html
cert-portal.siemens.com / productcert/html/ssa-082556.html
cems.fun / 2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html
ExploitPatchThird Party Advisory
github.com / krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f
Patch
web.mit.edu / kerberos/advisories
Vendor Advisory