CVE-2021-26557

Local privilege escalation via writable DLL directory

Published Oct 7, 2021 · Updated Aug 3, 2024

Local privilege escalation in Octopus Tentacle before 6.0.489 allows local users to gain privileged access through DLL side-loading. A custom Windows installation directory receives incorrect ACLs that grant BUILTIN\Users CreateFiles or AppendData rights, allowing a user-controlled DLL to enter the privileged service's load path. Exploitation requires a custom-location installation and local access; Linux installations and Octopus Cloud are outside the affected scope.

CVSS severity7.8
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Local privilege escalation in Octopus Tentacle before 6.0.489 allows local users to gain privileged access through DLL side-loading. A custom Windows installation directory receives incorrect ACLs that grant BUILTIN\Users CreateFiles or AppendData rights, allowing a user-controlled DLL to enter the privileged service's load path. Exploitation requires a custom-location installation and local access; Linux installations and Octopus Cloud are outside the affected scope.

The record

CVE
CVE-2021-26557
Published
Oct 7, 2021
Updated
Aug 3, 2024
Vendor
Octopus Deploy
Product
Octopus Tentacle
Classifications
CWE-426, CAPEC-38, T1574.001
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Oct 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.15.4 <unspecified
  2. Affected versionversion=unspecified <6.0.489

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Octopus Deploy · Octopus Tentacleversion=3.15.4 <unspecified; version=unspecified <6.0.489

Published CVSS scores

4.4NIST NVDAV:L/AC:M/Au:N/C:P/I:P/A:P
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-426Untrusted Search Path
CAPEC-38Leveraging/Manipulating Configuration File Search Paths
T1574.001Hijack Execution Flow: DLL

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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