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CVE-2026-28807: Gleam-Wisp Wisp Path Traversal (CVSS 8.7)

CVE-2026-28807 is a high severity path traversal in Gleam-Wisp Wisp with a CVSS score of 8.7. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Last updated: Jun 17, 2026

Quick answer

Direct answer

CVE-2026-28807 is a high severity path traversal in Gleam-Wisp Wisp with a CVSS score of 8.7. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Risk scores

CVSS base score
8.7HIGH
EPSS probability
1.06%
Higher than 64 percent of all CVEs
CISA KEV
Not listed
CVSS metricWhat it means
Attack vector (AV:N)Network: reachable remotely
Attack complexity (AC:L)Low complexity
Attack requirements (AT:N)No attack requirements
Privileges required (PR:N)No privileges required
User interaction (UI:N)No user interaction
Confidentiality (VC:H)High confidentiality impact
Integrity (VI:N)No integrity impact
Availability (VA:N)No availability impact

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

About Gleam-Wisp Wisp

CVE-2026-28807 affects Gleam-Wisp Wisp, a product from Gleam-Wisp. Before acting, confirm where Gleam-Wisp Wisp runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.

What the flaw is

In plain terms: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') vulnerability in gleam-wisp wisp allows arbitrary file read via percent-encoded path traversal. The wisp.serve_static function is vulnerable to path traversal because sanitization runs before percent-decoding. The encoded sequence %2e%2e passes through string.replace unchanged, then uri.percent_decode converts it to .., which the OS resolves as directory traversal when the file is read. An unauthenticated attacker can read any file readable by the application process in a single HTTP request, including application source code, configuration files, secrets, and system files. This issue affects wisp: from 2.1.1 before 2.2.1.

The weakness class is Path Traversal. An attacker can reach files outside the intended folder by tampering with a file path.

Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

Affected versions and timeline

FieldDetail
ProductGleam-Wisp Wisp
Affected versionsWisp from 2.1.1 before 2.2.1
PublishedMar 10, 2026
Last modifiedJun 17, 2026
Added to CISA KEVNot listed
Assigning CNA6b3ad84c-e1a6-4bf7-a703-f496b71e49db

How to detect it

  • Inventory every instance of Gleam-Wisp Wisp and record the running version against the affected range above.
  • Check external attack surface scans for internet facing instances of the component.
  • Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
  • Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.

How to fix it

  • Apply the fixed version of Gleam-Wisp Wisp named in the vendor advisory.
  • If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
  • Rescan after the change to prove the exposure is gone, then close the ticket.

CTEM action plan

CTEM stageWhat to do for this CVE
ScopeAdd every business service that depends on Gleam-Wisp Wisp to the current CTEM cycle.
DiscoverFind all instances, including shadow and cloud deployments, and record versions and exposure.
PrioritizeRank using EPSS and CVSS together with asset exposure and business impact.
ValidateConfirm the flaw is reachable and exploitable in your environment and that compensating controls work.
MobilizeAssign the fix to the asset owner with a due date matched to the priority, then verify closure.

CWE References

Technical References

Frequently asked questions

CVE-2026-28807 is a high severity path traversal in Gleam-Wisp Wisp with a CVSS score of 8.7. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.

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