In MIT Kerberos 5 (aka krb5) 1.7 and later, an authenticated attacker can cause a KDC assertion failure by sending invalid S4U2Self or S4U2P
In MIT Kerberos 5 (aka krb5) 1.7 and later, an authenticated attacker can cause a KDC assertion failure by sending invalid S4U2Self or S4U2Proxy requests.
- Published
- Aug 9, 2017
- Updated
- Jun 16, 2026
- EPSS
- 2.4% · 83th percentile
- CWE
- CWE-617
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Report tools
Action score
27
Monitor
Low priority for now.
- CVSS
- 26 / 40 · 6.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 2.4%
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| mit | kerberos | cpe:2.3:a:mit:kerberos |
| mit | kerberos 5 | cpe:2.3:a:mit:kerberos_5 |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- fedoraproject fedora25
- fedoraproject fedora26
- mit kerberos5-1.13.7
- mit kerberos 51.10
- mit kerberos 51.10.1
- mit kerberos 51.10.2
- mit kerberos 51.10.3
- mit kerberos 51.10.4
- mit kerberos 51.11
- mit kerberos 51.11.1
- mit kerberos 51.11.2
- mit kerberos 51.11.3
- mit kerberos 51.11.4
- mit kerberos 51.11.5
- mit kerberos 51.12
- mit kerberos 51.12.1
- mit kerberos 51.12.2
- mit kerberos 51.12.3
- mit kerberos 51.13
- mit kerberos 51.13.1
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | krb5 | before 1.15.1-2 | 1.15.1-2 |
| Debian:7 | krb5 | before 1.10.1+dfsg-5+deb7u8 | 1.10.1+dfsg-5+deb7u8 |
| openSUSE:Tumbleweed | krb5 | before 1.19.2-2.2 | 1.19.2-2.2 |
| Red Hat:enterprise_linux:7::client | krb5 | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | krb5-debuginfo | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | krb5-devel | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | krb5-libs | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | krb5-pkinit | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | krb5-server | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | krb5-server-ldap | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | krb5-workstation | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
| Red Hat:enterprise_linux:7::client | libkadm5 | before 0:1.15.1-18.el7 | 0:1.15.1-18.el7 |
Same product
mit: all recordsOther highest-scoring records for the same primary product.
- CVE-2001-0554Buffer overflow in BSD-based telnetd telnet daemon on various operating systems allows remote attackers to execute arbitrary commands via a 52Plan
- CVE-2004-0523Multiple buffer overflows in krb5_aname_to_localname for MIT Kerberos 5 (krb5) 1.3.3 and earlier allow remote attackers to execute arbitrary43Plan
- CVE-2009-4212Multiple integer underflows in the (1) AES and (2) RC4 decryption functionality in the crypto library in MIT Kerberos 5 (aka krb5) 1.3 throu42Plan
- CVE-2010-0283The Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.7 before 1.7.2, and 1.8 alpha, allows remote attackers to cause a denial of32Monitor
- CVE-2018-5709An issue was discovered in MIT Kerberos 5 (aka krb5) through 1.16.31Monitor
- CVE-2003-0138Version 4 of the Kerberos protocol (krb4), as used in Heimdal and other packages, allows an attacker to impersonate any principal in a realm31Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:krb5 | 1.15.1-2 · Debian:12 | Package registry (OSV) |
| opensuse:krb5 | 1.19.2-2.2 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:krb5 | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:krb5-debuginfo | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:krb5-devel | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:krb5-libs | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:krb5-pkinit | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:krb5-server | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:krb5-server-ldap | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:krb5-workstation | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
| red hat:libkadm5 | 0:1.15.1-18.el7 · Red Hat:enterprise_linux:7::client | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
CWE-617 · Reachable AssertionCVSS vector
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
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References
- www.securityfocus.com/bid/100291
- access.redhat.com/errata/RHSA-2018:0666
- github.com/krb5/krb5/commit/ffb35baac6981f9e8914f8f3bffd37f284b85970
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4HNWXM6OQU7G23MG7XWIOBRGP43ECLDT/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UBUTXMNZWMVJLQ4NDX5OQFPUVCJRLV3W/
Vendor advisories and official records. Exploit/PoC links are deliberately left out.