Security readout for executives and security teams
Plain-English summary
CVE-2021-26092 is a reflected cross-site scripting issue in Fortinet SSL VPN web portal error pages. An attacker could trick a user into opening a malicious request that runs attacker-controlled script in the portal context. Business risk is moderate because exploitation requires user interaction, but affected systems are often internet-facing access infrastructure.
Executive priority
Treat this as moderate urgency. It is not a cited active exploitation case, but it affects remote access infrastructure. Remediate promptly for internet-facing VPN portals, especially where legacy FortiOS or FortiProxy versions remain in service.
Technical view
FortiOS and FortiProxy failed to sanitize malicious GET parameters sent to the SSL VPN web portal error page. The CVSS 3.1 score is 4.7 with network attack vector, low complexity, no privileges required, and user interaction required. The impact cited is low integrity impact with changed scope.
Likely exposure
Exposure is most likely where affected FortiOS or FortiProxy versions have SSL VPN web portals reachable by users or the internet. The vulnerable FortiOS ranges span 5.2.10-6.4.4 branches listed in the CVE, and FortiProxy 1.2.0-2.0.1 ranges listed in the CVE.
Exploitation context
The provided sources do not state active exploitation, and the CVE is not marked KEV. The attack is reflected XSS: a victim must interact with a crafted request or link. Do not assume compromise from presence alone; validate version and portal exposure.
Researcher notes
Evidence is limited to the CVE record and Fortinet PSIRT reference in the source bundle. The sources identify reflected XSS via malicious GET parameters on the SSL VPN error page but do not provide exploit details, observed exploitation, or fixed-version specifics in the supplied text.
Mitigation direction
- Check Fortinet FG-IR-20-199 for official remediation guidance and fixed versions.
- Prioritize remediation for internet-facing SSL VPN portals.
- Upgrade affected FortiOS and FortiProxy systems according to Fortinet guidance.
- Limit SSL VPN portal exposure where operationally feasible.
- Retire or isolate unsupported affected branches if upgrade is not immediately possible.
Validation and detection
- Inventory FortiOS and FortiProxy versions across perimeter devices.
- Compare versions against the vulnerable ranges in the CVE record.
- Identify which SSL VPN web portals are internet-facing.
- Confirm remediation status against Fortinet FG-IR-20-199.
- Review web logs for unusual error-page GET requests with script-like parameters.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CVE-2021-26092 mapping review
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Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N/E:F/RL:X/RC:X
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N/E:F/RL:X/RC:X2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.7MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N/E:F/RL:X/RC:X
Source materials
- CVE List V5 sourceCVE List V5
- https://fortiguard.com/psirt/FG-IR-20-199CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.