An authentication bypass flaw was found in the way krb5's certauth interface before 1.16.1 handled the validation of client certificates.
An authentication bypass flaw was found in the way krb5's certauth interface before 1.16.1 handled the validation of client certificates. A remote attacker able to communicate with the KDC could potentially use this flaw to impersonate arbitrary principals under rare and erroneous circumstances.
- Published
- Jul 26, 2018
- Updated
- Jun 16, 2026
- EPSS
- 3.3% · 88th percentile
- CWE
- CWE-287
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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 · 3.3%
CNA vs NVD score
- NVD
- 6.5
- CNA · redhat
- 6.5
- agree
CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| redhat | enterprise linux | cpe:2.3:o:redhat:enterprise_linux |
| redhat | enterprise linux desktop | cpe:2.3:o:redhat:enterprise_linux_desktop |
| redhat | enterprise linux server | cpe:2.3:o:redhat:enterprise_linux_server |
| redhat | enterprise linux workstation | cpe:2.3:o:redhat:enterprise_linux_workstation |
| mit | kerberos 5 | cpe:2.3:a:mit:kerberos_5 |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- mit kerberos 51.0 and later · before 1.16.1
- redhat enterprise linux7.0
- redhat enterprise linux desktop7.0
- redhat enterprise linux server7.0
- redhat enterprise linux workstation7.0
Versions reported by the vendor
Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.
MIT krb5
- 1.16.1affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| 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 |
| SUSE:Linux Enterprise Server for SAP Applications 12 SP1 | krb5 | before 1.12.1-38.5.3 | 1.12.1-38.5.3 |
Same product
redhat: all recordsOther highest-scoring records for the same primary product.
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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 |
|---|---|---|
| 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) |
| suse:krb5 | 1.12.1-38.5.3 · SUSE:Linux Enterprise Server for SAP Applications 12 SP1 | 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
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
CWE-287 · Improper AuthenticationCVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
nvd-primary
Root cause
Authentication is added route by route instead of being enforced in one place. When a route added later bypasses the shared middleware, the session check never runs for it.
The bug in code
The whole CWE-287 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
app.use("/admin", requireSession, adminRouter);
// Route added later skips the middlewareapp.post("/admin-api/config", updateConfig);Fixed
const admin = express.Router();admin.use(requireSession, requireRole("admin"));
admin.post("/config", updateConfig);app.use("/admin", admin);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
- Authentication AbuseCAPEC-114Medium
- Authentication BypassCAPEC-115Medium
- Identity SpoofingCAPEC-151likelihood: Medium · Medium
- Fake the Source of DataCAPEC-194Medium
- Exploiting Trust in ClientCAPEC-22likelihood: High · High
- Utilizing REST's Trust in the System Resource to Obtain Sensitive DataCAPEC-57likelihood: Medium · Very High
- Session HijackingCAPEC-593likelihood: High · Very High
- Token ImpersonationCAPEC-633Medium
ATT&CK techniques
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✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- www.securityfocus.com/bid/100511
- access.redhat.com/errata/RHSA-2018:0666
- bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-7562
- github.com/krb5/krb5/pull/694
- github.com/krb5/krb5/pull/694/commits/1de6ca2f2eb1fdbab51f1549a25a6903aefcc196
- github.com/krb5/krb5/pull/694/commits/50fe4074f188c2d4da0c421e96553acea8378db2
- github.com/krb5/krb5/pull/694/commits/b7af544e50a4d8291524f590e20dd44430bf627d
Vendor advisories and official records. Exploit/PoC links are deliberately left out.