Simple Machines Forum Authorization Bypass via AttachmentApprove.php
Summary
| CVE | CVE-2026-39903 |
|---|---|
| State | PUBLISHED |
| Assigner | VulnCheck |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-10 17:16:57 UTC |
| Updated | 2026-07-14 21:16:46 UTC |
| Description | Simple Machines Forum 2.1 prior to commit 7d048f8 and 3.0 prior to commit a7875e8 contains an authorization bypass vulnerability in Sources/Actions/AttachmentApprove.php where a single-character operator error causes the permission check to always pass regardless of user permissions. An authenticated low-privileged user can approve, reject, or delete any pending attachments on any board without holding the required approve_posts permission, bypass moderation queues for their own uploads, and enumerate and delete other users' pending attachments. |
Risk And Classification
Primary CVSS: v4.0 7.1 HIGH from [email protected]
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/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
EPSS: 0.003330000 probability, percentile 0.254570000 (date 2026-07-15)
Problem Types: CWE-863 | CWE-863 Incorrect Authorization
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 7.1 | HIGH | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 7.1 | HIGH | CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N |
| 3.1 | [email protected] | Secondary | 7.1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L |
| 3.1 | CNA | CVSS | 7.1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
LowAttack Requirements
NonePrivileges Required
LowUser Interaction
NoneConfidentiality
NoneIntegrity
HighAvailability
LowSub Conf.
NoneSub Integrity
NoneSub Availability
NoneCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:L/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
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
HighAvailability
LowCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | SimpleMachines | SMF | affected 2.1.0 2.1.7 semver | Not specified |
| CNA | SimpleMachines | SMF | unaffected 7d048f8d66aab9af51cd6ee110fbad103cf673e8 git | Not specified |
| CNA | SimpleMachines | SMF | affected 3.0.0 semver | Not specified |
| CNA | SimpleMachines | SMF | unaffected a7875e876a647572dd4c45da881b875092caac3d git | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/SimpleMachines/SMF/pull/9181 | [email protected] | github.com | |
| www.vulncheck.com/advisories/simple-machines-forum-authorization-bypass-via-att... | [email protected] | www.vulncheck.com | |
| github.com/SimpleMachines/SMF/pull/9182 | [email protected] | github.com | |
| github.com/SimpleMachines/SMF/commit/a7875e876a647572dd4c45da881b875092c... | [email protected] | github.com | |
| github.com/SimpleMachines/SMF/commit/7d048f8d66aab9af51cd6ee110fbad103cf... | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Elure (Marasescu Mihnea-Luca) (en)
CNA: VulnCheck (en)
There are currently no legacy QID mappings associated with this CVE.