High severity · published Apr 28, 2026
CVE-2026-40355
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…
7.5
CVSS
0.6%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 51% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
K5
Kerberos 5 · MIT
1.18 before 1.22.3 · source: vendor, NVD
SS
SIMATIC S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.6; V3.1.5; V3.1.7; V3.1.6; V3.1.5; V3.1.7 · source: CISA
SS
SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP · Siemens
V3.1.6; V3.1.5; V3.1.7; V3.1.6; V3.1.5; V3.1.7 · source: CISA
SS
SIPLUS S7-1500 CPU 1518-4 PN/DP MFP · Siemens
V3.1.6; V3.1.5; V3.1.7 · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-40355
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-40355
Exploit
https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html
Patch
https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f
Vendor Advisory
https://web.mit.edu/kerberos/advisories/
cert-portal.siemens.com
https://cert-portal.siemens.com/productcert/html/ssa-019113.html
cert-portal.siemens.com
https://cert-portal.siemens.com/productcert/html/ssa-082556.html
cert-portal.siemens.com
https://cert-portal.siemens.com/productcert/html/ssa-457936.html
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