myBB 1.6.4 Backdoor Arbitrary Command Execution
Published Aug 13, 2025
10.0
CRITICALCVSS 4.0
EPSS 1.98%
Description
myBB version 1.6.4 was distributed with an unauthorized backdoor embedded in the source code. The backdoor allowed remote attackers to execute arbitrary PHP code by injecting payloads into a specially crafted collapsed cookie. This vulnerability was introduced during packaging and was not part of the intended application logic. Exploitation requires no authentication and results in full compromise of the web server under the context of the web application.
Affected products
-
- Version 1.6.4StatusaffectedConstraints-
- Version
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| myBB Group | Forum Software | unaffected |
|
No data.
No Red Hat product state for this CVE.
No package ranges for this CVE.
Remediation
No remediation recorded yet.
Metrics
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
1 other source (NVD) ▾
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
No CVSS v3.0 score for this CVE.
No CVSS v2.0 score for this CVE.
This CVE is not in the KEV list.
CISA SSVC (Vulnrichment)
Stakeholder-Specific Vulnerability Categorization from CISA ADP.
Exploitation
PoCAutomatable
YesTechnical Impact
TotalDecision
n/aAssessed Aug 14, 2025 · SSVC 2.0.3
Estimated probability of exploitation in the wild in the next 30 days (FIRST EPSS). As of Oct 1, 2026.
Score over time
2025–2026- EPSS v4
- EPSS v5
Percentile over time
- EPSS v4
- EPSS v5
Table of values (8 key points)
Flat stretches are collapsed; showing up to 120 newest points.
| Date | Score | Percentile | Model |
|---|---|---|---|
| Oct 1, 2026 | 1.98% (0.01977) | 79.75th | v5 (v2026.06.15) |
| Jun 15, 2026 | 1.86% (0.01860) | 76.41th | v5 (v2026.06.15) |
| Jun 9, 2026 | 68.12% (0.68122) | 98.61th | v4 (v2025.03.14) |
| Jan 10, 2026 | 53.00% (0.53002) | 97.86th | v4 (v2025.03.14) |
| Jan 9, 2026 | 44.46% (0.44459) | 97.44th | v4 (v2025.03.14) |
| Dec 13, 2025 | 51.63% (0.51626) | 97.77th | v4 (v2025.03.14) |
| Oct 8, 2025 | 47.45% (0.47454) | 97.54th | v4 (v2025.03.14) |
| Aug 14, 2025 | 0.26% (0.00262) | 49.37th | v4 (v2025.03.14) |
References (5)
- https://blog.mybb.com/2011/10/06/1-6-4-security-vulnerabilit/ vendor-advisorypatchVendor Advisory
- https://raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/exploits/unix/webapp/mybb_backdoor.rb exploitProduct
- https://web.archive.org/web/20111015224948/http://secunia.com/advisories/46300/ third-party-advisoryThird Party Advisory
- https://www.exploit-db.com/exploits/17949 exploit
- https://www.vulncheck.com/advisories/mybb-backdoor-arbitrary-command-execution third-party-advisoryThird Party Advisory
| Link | Providers | Tags |
|---|---|---|
| https://blog.mybb.com/2011/10/06/1-6-4-security-vulnerabilit/ | vendor-advisorypatchVendor Advisory | |
| https://raw.githubusercontent.com/rapid7/metasploit-framework/master/modules/exploits/unix/webapp/mybb_backdoor.rb | exploitProduct | |
| https://web.archive.org/web/20111015224948/http://secunia.com/advisories/46300/ | third-party-advisoryThird Party Advisory | |
| https://www.exploit-db.com/exploits/17949 | exploit | |
| https://www.vulncheck.com/advisories/mybb-backdoor-arbitrary-command-execution | third-party-advisoryThird Party Advisory |
Change history (0)
No recorded changes yet.