MIT Kerberos 5 up to 1.22.2 /etc/gss/mech gss_accept_sec_context integer underflow

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.4$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as critical, was found in MIT Kerberos 5 up to 1.22.2. This affects the function gss_accept_sec_context of the file /etc/gss/mech. The manipulation results in integer underflow. This vulnerability was named CVE-2026-40356. The attack may be performed from remote. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in MIT Kerberos 5 up to 1.22.2. Affected is the function gss_accept_sec_context of the file /etc/gss/mech. The manipulation with an unknown input leads to a integer underflow vulnerability. CWE is classifying the issue as CWE-191. The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. This is going to have an impact on availability. CVE summarizes:

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 registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, possibly causing the process to terminate in parse_message.

The advisory is shared for download at web.mit.edu. This vulnerability is traded as CVE-2026-40356 since 04/11/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 07/08/2026).

The vulnerability scanner Nessus provides a plugin with the ID 311064 (Fedora 45 : krb5 (2026-2e9fe57a46)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.22.3 eliminates this vulnerability.

The vulnerability is also documented in the databases at CNNVD (CNNVD-202604-5565), Tenable (311064) and CERT Bund (WID-SEC-2026-1290). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

  • Red Hat Enterprise Linux
  • Fedora Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • RESF Rocky Linux
  • IBM MQ
  • MIT Kerberos
  • Debian Linux
  • IBM QRadar SIEM

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.4
VulDB Meta Temp Score: 6.4

VulDB Base Score: 5.9
VulDB Temp Score: 5.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 7.5
NVD Vector: 🔒

CNA Base Score: 5.9
CNA Vector (MITRE): 🔒

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Integer underflow
CWE: CWE-191 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Nessus ID: 311064
Nessus Name: Fedora 45 : krb5 (2026-2e9fe57a46)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kerberos 5 1.22.3

Timelineinfo

04/11/2026 CVE reserved
04/28/2026 +17 days Advisory disclosed
04/28/2026 +0 days VulDB entry created
07/08/2026 +71 days VulDB entry last update

Sourcesinfo

Vendor: mit.edu

Advisory: web.mit.edu
Status: Confirmed

CVE: CVE-2026-40356 (🔒)
GCVE (CVE): GCVE-0-2026-40356
GCVE (VulDB): GCVE-100-359928
CERT Bund: WID-SEC-2026-1290 - MIT Kerberos: Mehrere Schwachstellen ermöglichen Denial of Service
CNNVD: CNNVD-202604-5565 - MIT Kerberos 数字错误漏洞

Entryinfo

Created: 04/28/2026 08:42
Updated: 07/08/2026 15:55
Changes: 04/28/2026 08:42 (65), 04/29/2026 21:38 (6), 04/30/2026 07:27 (2), 06/20/2026 07:58 (7), 07/08/2026 15:55 (11)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Interested in the pricing of exploits?

See the underground prices here!