hugo: Improper Handling of Case Sensitivity
CVE-2026-100693 is a high-severity improper handling of case sensitivity vulnerability in hugo from Gohugoio, with a CVSS 3.1 base score of 8.4 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. The record lists version 0.166.0 as the first without the flaw, so updating hugo to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.14% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update hugo to 0.166.0 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.6 | High | CNA (vulncheck.com) |
| CVSS 3.1 | 8.4 | High | CNA (vulncheck.com) |
Official description
Hugo versions from v0.162.0 before v0.166.0 contain a case-sensitive validation flaw in the security.http.urls IP-literal deny rule that allows attackers to bypass restrictions. Attackers can use mixed-case URL schemes in resources.GetRemote calls to fetch from restricted IP addresses like localhost.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Handling of Case Sensitivity
The product does not properly account for differences in case sensitivity when accessing or determining the properties of a resource, leading to inconsistent results.
How developers prevent this class of flaw
- Avoid making decisions based on names of resources (e.g. files) if those resources can have alternate names.
- Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174). Such errors could be used to bypass allowlist validation schemes by introducing dangerous inputs after they have been checked.
More Improper Handling of Case Sensitivity vulnerabilities (CWE-178)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- vulncheck.com/advisories/hugo-0.162.0-before-0.166.0-ip-literal-deny-rule-bypassThird Party Advisory
Other vulnerabilities in hugo
- 7.5 High severity
- 7.5 High severity
- 9.8 Critical severity
- 7.4 High severity
- 8.6 High severity
- 8.1 High severity
Recent Improper Handling of Case Sensitivity vulnerabilities
- 7.5 High severity
- 8.8 High severity
- 7.5 High severity
- 8.1 High severity
- 7.5 High severity
- 8.1 High severity
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