Evidence used
- No CISA KEV confirmation is currently recorded.
- EPSS is 0.56% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2026
CVE-2025-53844High confidence
Fortinet FortiOS: Out-of-bounds Write
Fortinet · FortiOS
Official source articles: Siemens SSA-864900 ↗ · Fortinet FG-IR-26-123 ↗. Check the applicable product and release in the original source.
8.3HighCVSS 3.1
Patch only the product branches with a verified fix
Fix availability varies by productHigh technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs Fortinet FortiOS and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Remediation availability differs by product scope
Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
- Siemens ProductCERT: 1 affected or under-investigation product state without a fixed product state in the same current advisory
Direct vendor intelligence
1 currentAuthoritative vendor CSAF and VEX advisories
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
SSA-864900 · CSAF 2.0 · revision 11 · finalSiemens ProductCERTSSA-864900: Multiple Vulnerabilities in Fortigate NGFW on RUGGEDCOM APE1808 Devices
The vendor explicitly identifies these products as affected by this CVE.
- RUGGEDCOM APE1808 with Fortinet NGFW < V7.6.6
- Summary
- A out-of-bounds write vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11 allows attacker to execute unauthorized code or commands via specially crafted packets.
- Remediation
- Update Fortigate NGFW to V7.6.6 or later following the secure update recommendation procedure. Contact customer support to receive detailed information
High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 1 structured product or package state remain unresolved. Apply remediation only to the exact product branch confirmed by its source.
Fix availability varies by product01
What, why and how
A out-of-bounds write vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11 allows attacker to execute unauthorized code or commands via specially crafted packets.
What
A out-of-bounds write vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11 allows attacker to execute unauthorized code or commands via specially crafted packets.
Why
A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
A out-of-bounds write vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2.0 through 7.2.11 allows attacker to execute unauthorized code or commands via specially crafted packets.
Why
A bounds error lets data be written beyond the intended memory region, potentially corrupting control data.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Out-of-bounds Write → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- Low: a basic authenticated account is required
- User interaction
- None
- Attack complexity
- Low: no specialised conditions are recorded
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-787 ↗
CWE-787: Out-of-bounds Write. The product writes data past the end, or before the beginning, of the intended buffer.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:CCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.AHighAvailability impact: A successful attack can cause a major loss.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Fix availability varies by product
- Fixed
- Upgrade to FortiOS version 7.6.4 or above
- Upgrade to FortiOS version 7.4.9 or above
- Upgrade to FortiOS version 7.2.12 or above
- Upgrade to FortiOS version 7.0.18 or above
- Fortinet remediated this issue in FortiSASE version 25.3.a and hence customers do not need to perform any action.
- Upgrade to FortiSwitchManager version 7.2.7 or above
- Upgrade to FortiSwitchManager version 7.0.6 or above
- Fortinet remediated this issue in FortiEdgeCloud version 25.3 and hence customers do not need to perform any action.
- Action
- Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
Official vendor articles1 stored document
Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.
- PSIRT | FortiGuard Labs →Original publisher ↗Searchable text snapshot · Captured 29 Sep 2026PSIRT Out-of-bounds access in CAPWAP daemon Summary An Out-Of-Bounds Write vulnerability [CWE-787] in FortiOS capwap daemon may allow an attacker controlling an authenticated FortiAP FortiExtender or FortiSwitch to gain execution privileges on the FortiGate device Version Affected Solution FortiOS 8.0 Not affected
04
Evidence and provenance
Published 12 May 2026 · Last source change 11 Aug 2026, 12:23 UTC · CWE-787 · Out-of-bounds Write
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2025-209802
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceCNA
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Vendor guidanceAuthoritative vendor guidance changed: added remediation: fortiguard.fortinet.com/FG-IR-26-123; removed patch: cert-portal.siemens.com/ssa-864900.html; removed remediation: cert-portal.siemens.com/ssa-864900.html.psirt@fortinet.com ↗
- Before
- patch: cert-portal.siemens.com/ssa-864900.html · remediation: cert-portal.siemens.com/ssa-864900.html · vendor advisory: fortiguard.fortinet.com/FG-IR-26-123
- After
- remediation: fortiguard.fortinet.com/FG-IR-26-123 · vendor advisory: fortiguard.fortinet.com/FG-IR-26-123
- Affected versionsThe structured affected or fixed version information changed.CNA ↗
- Before
- 7.6.0 ≤ 7.6.3; 7.4.0 ≤ 7.4.8; 7.2.0 ≤ 7.2.11; 7.0.0 ≤ 7.0.17; 6.4.0 ≤ 6.4.16; 6.2.0 ≤ 6.2.17; 6.0.0 ≤ 6.0.18 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
- After
- FortiOS: 7.6.0 ≤ 7.6.3, 7.4.0 ≤ 7.4.8, 7.2.0 ≤ 7.2.11, 7.0.0 ≤ 7.0.17, 6.4.0 ≤ 6.4.16, 6.2.0 ≤ 6.2.17, 6.0.0 ≤ 6.0.18 · Fixed: Upgrade to FortiOS version 7.6.4 or above; Upgrade to FortiOS version 7.4.9 or above; Upgrade to FortiOS version 7.2.12 or above; Upgrade to FortiOS version 7.0.18 or above; Fortinet remediated this issue in FortiSASE version 25.3.a and hence customers do not need to perform any action.; Upgrade to FortiSwitchManager version 7.2.7 or above; Upgrade to FortiSwitchManager version 7.0.6 or above; Fortinet remediated this issue in FortiEdgeCloud version 25.3 and hence customers do not need to perform any action.
- Remediation statusRemediation status changed from Mitigation available to Patch available.psirt@fortinet.com ↗
- Before
- Mitigation available
- After
- Patch available
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.Siemens ProductCERT ↗
- Before
- Awaiting fix
- After
- Mitigation available
CVE published
Fixed release or patch reference recorded
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.