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CVE Record

CVE-2021-26473: Unauthenticated arbitrary file upload and command execution in Vembu products

In VembuBDR before 4.2.0.1 and VembuOffsiteDR before 4.2.0.1 the http API located at /sgwebservice_o.php action logFilePath allows an attacker to write arbitrary files in the context of the web server process. These files can then be executed remotely by calling the file via the web server.

CriticalCVSS 9.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

This is a critical unauthenticated remote code execution issue in older Vembu backup products. An attacker who can reach the affected web API may write files as the web server and then cause those files to run. Backup systems are high-value targets, so exposed legacy deployments need urgent attention.

Executive priority

Treat this as urgent for any legacy Vembu backup deployment. Backup infrastructure often has privileged access to sensitive systems, and this flaw can allow unauthenticated remote code execution when exposed.

Technical view

VembuBDR and VembuOffsiteDR before 4.2.0.1 expose an HTTP API behavior involving /sgwebservice_o.php and logFilePath that allows arbitrary file writes in the web server process context. The CVE description says written files can then be executed remotely through the web server.

Likely exposure

Exposure is most likely where VembuBDR or VembuOffsiteDR versions before 4.2.0.1 are reachable over a network, especially from the internet. The bundle does not provide CPEs or a complete product inventory mapping.

Exploitation context

The CVSS 9.8 rating reflects network access, low complexity, no authentication, and no user interaction. KEV is false, and the provided bundle does not prove active in-the-wild exploitation. Public references describe Vembu zero-days, but exploit status is not established here.

Researcher notes

The bundle lacks CWE classification, CPEs, and detailed vendor remediation notes beyond affected version boundaries. Analysis should remain anchored to confirmed affected products and versions, with no assumptions about other Vembu products or current exploitation.

Mitigation direction

  • Upgrade VembuBDR and VembuOffsiteDR to 4.2.0.1 or later.
  • Restrict access to Vembu web and API interfaces to trusted administrative networks.
  • Review vendor and CSIRT guidance for any additional hardening or recovery instructions.
  • Prioritize backup server containment if compromise indicators are found.

Validation and detection

  • Inventory all VembuBDR and VembuOffsiteDR instances and record versions.
  • Confirm no deployment is running a version before 4.2.0.1.
  • Check whether Vembu web interfaces are internet-exposed or broadly reachable internally.
  • Review web server and application logs for suspicious file writes or unexpected web-accessible files.
  • Validate backups and administrative credentials if the host may have been exposed.
Prepared
Confidence
high
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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.

description · low confidence lookup

File 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 lookup
cve · low confidence lookup

CVE-2021-26473 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
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

Official CVE source material

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.

1CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
9.8CVSS 3.1CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

9.8Critical
CVSS 3.1 vector shape for CVE-2021-26473Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.