Security readout for executives and security teams
Plain-English summary
This CVE affects Yupoxion BearAdmin instances before the referenced commit. An unauthenticated attacker could abuse a file upload function to run code on the server. That can lead to full system compromise, but the supplied sources do not show active exploitation or complete product version metadata.
Executive priority
Treat this as urgent for any confirmed BearAdmin deployment, especially internet-facing systems. The business risk is potential server takeover without authentication. If BearAdmin is not present, document non-exposure and continue normal monitoring.
Technical view
CVE-2021-35261 is a CWE-434 unrestricted file upload flaw in BearAdmin’s Upfile function under extend/tools/Ueditor. The CVSS 3.1 score is 9.8 because exploitation is network-reachable, low complexity, unauthenticated, and can affect confidentiality, integrity, and availability.
Likely exposure
Exposure is likely limited to organizations running Yupoxion BearAdmin code before commit 10176153528b0a914eb4d726e200fd506b73b075. The source bundle lists no CPEs, vendor versions, package names, or hosted-service indicators, so asset confirmation is required.
Exploitation context
The CVE is not marked as CISA KEV in the supplied data, and no cited source claims active exploitation. Risk remains high because the described flaw is unauthenticated remote code execution through a public upload endpoint.
Researcher notes
The public CVE data gives a clear vulnerable function and endpoint, but affected product metadata is weak: vendor, product, versions, and CPEs are listed as n/a. Validate against source repository history and the linked GitHub issue before scoping broadly.
Mitigation direction
- Inventory BearAdmin deployments and identify their exact commit or release state.
- Update to code at or after the referenced commit, if vendor guidance confirms it.
- Restrict public access to extend/tools/Ueditor where business use does not require it.
- Disable the vulnerable upload path until remediation is verified.
- Review vendor issue and CVE records for updated remediation guidance.
Validation and detection
- Confirm whether any internet-facing application uses yupoxiong/BearAdmin.
- Verify deployed code is not older than commit 10176153528b0a914eb4d726e200fd506b73b075.
- Check routing and proxy rules for public reachability of extend/tools/Ueditor.
- Review web logs for unexpected upload activity against the Ueditor endpoint.
- Confirm uploaded files cannot execute as server-side code.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-434: File access and web shell behavior lookup
File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-35261 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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:N/S:U/C:H/I:H/A:H3.95.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/yupoxiong/BearAdmin/issues/16CVE reference
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.