Common Weakness Enumeration

CWE-515

Weakness Allowed

Covert Storage Channel

Abstraction: Base · Status: Incomplete

A covert storage channel transfers information through the setting of bits by one program and the reading of those bits by another. What distinguishes this case from that of ordinary operation is that the bits are used to convey encoded information.

Covert storage channels occur when out-of-band data is stored in messages for the purpose of memory reuse. Covert channels are frequently classified as either storage or timing channels. Examples would include using a file intended to hold only audit information to convey user passwords--using the name of a file or perhaps status bits associated with it that can be read by all users to signal the contents of the file. Steganography - concealing information in such a manner that no one but the intended recipient knows of the existence of the message - is a good example of a covert storage channel.

Mapping guidance

This CWE entry is at the Base level of abstraction, which is a preferred level of abstraction for mapping to the root causes of vulnerabilities.

Carefully read both the name and description to ensure that this mapping is an appropriate fit. Do not try to 'force' a mapping to a lower-level Base/Variant simply to comply with this preferred level of abstraction.

Relationships and members
ChildOf: CWE-514 · View CWE-1000
Modes of introduction
Implementation
Notes

Maintenance

As of CWE 4.9, members of the CWE Hardware SIG are working to improve CWE's coverage of transient execution weaknesses, which include issues related to Spectre, Meltdown, and other attacks that create or exploit covert channels. As a result of that work, this entry might change in CWE 4.10.

Content history
Submission: Landwehr · 2006-07-19 · CWE Draft 3
Modification: Eric Dalci · Cigital · 2008-07-01 · CWE 1.0

updated Time_of_Introduction

Modification: CWE Content Team · MITRE · 2008-09-08 · CWE 1.0

updated Common_Consequences, Relationships, Other_Notes, Taxonomy_Mappings

Modification: CWE Content Team · MITRE · 2008-10-14 · CWE 1.0.1

updated Description

Modification: CWE Content Team · MITRE · 2009-07-27 · CWE 1.5

updated Common_Consequences, Description

Modification: CWE Content Team · MITRE · 2009-10-29 · CWE 1.6

updated Other_Notes

Modification: CWE Content Team · MITRE · 2011-06-01 · CWE 1.13

updated Common_Consequences

Modification: CWE Content Team · MITRE · 2012-05-11 · CWE 2.2

updated Relationships

Modification: CWE Content Team · MITRE · 2014-07-30 · CWE 2.8

updated Relationships

Modification: CWE Content Team · MITRE · 2020-02-24 · CWE 4.0

updated Relationships

Modification: CWE Content Team · MITRE · 2022-10-13 · CWE 4.9

updated Maintenance_Notes

Modification: CWE Content Team · MITRE · 2023-04-27 · CWE 4.11

updated Relationships

Modification: CWE Content Team · MITRE · 2023-06-29 · CWE 4.12

updated Mapping_Notes

Modification: CWE Content Team · MITRE · 2024-07-16 · CWE 4.15

updated References

Modification: CWE Content Team · MITRE · 2025-12-11 · CWE 4.19

updated Applicable_Platforms, Weakness_Ordinalities

Modification: CWE Content Team · MITRE · 2026-10-28 · CWE 5.0

updated Description

2 vulnerabilities reference this CWE, most recent first.

CVE-2026-54316 (GCVE-0-2026-54316)

Vulnerability from cvelistv5 – Published: 2026-06-23 17:06 – Updated: 2026-06-23 17:37
VLAI
Title
Claude Code: Out-of-Band Data Exfiltration via Pre-Approved HuggingFace Domain in WebFetch
Summary
Claude Code is an agentic coding tool. From 0.2.54 until 2.1.163, because the hostname huggingface.co was pre-approved as a bare hostname for the WebFetch tool, any path on that domain—including attacker-controlled model repositories—was auto-approved without a permission prompt or being subject to --allowedTools restrictions. An attacker able to inject untrusted content into a Claude Code context could direct it to issue WebFetch requests against attacker-controlled repository files (e.g. /resolve/main/config.json), which HuggingFace counts as downloads server-side, creating a covert out-of-band channel for encoding and exfiltrating data Claude can access such as files, environment variables, or command output. Reliably exploiting this required the ability to add untrusted content into a Claude Code context window. This vulnerability is fixed in 2.1.163.
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-23 17:37 UTC
CWE
  • CWE-183 - Permissive List of Allowed Inputs
  • CWE-200 - Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-515 - Covert Storage Channel
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7895 records in the last 180 days details
References
Impacted products
Vendor Product Version
anthropics claude-code Affected: >= 0.2.54, < 2.1.163
Create a notification for this product.
Show details on NVD website

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                "timestamp": "2026-06-23T17:37:32.464559Z",
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GHSA-FG94-H982-F3MM

Vulnerability from github – Published: 2026-06-17 18:06 – Updated: 2026-07-20 21:10
VLAI
Summary
Claude Code: Out-of-Band Data Exfiltration via Pre-Approved HuggingFace Domain in WebFetch
Details

Because the hostname huggingface.co was pre-approved as a bare hostname for the WebFetch tool, any path on that domain—including attacker-controlled model repositories—was auto-approved without a permission prompt or being subject to --allowedTools restrictions. An attacker able to inject untrusted content into a Claude Code context could direct it to issue WebFetch requests against attacker-controlled repository files (e.g. /resolve/main/config.json), which HuggingFace counts as downloads server-side, creating a covert out-of-band channel for encoding and exfiltrating data Claude can access such as files, environment variables, or command output. Reliably exploiting this required the ability to add untrusted content into a Claude Code context window. Users on standard Claude Code auto-update have received this fix already; users performing manual updates are advised to update to the latest version.

Thank you to hackerone.com/novee for reporting this issue.

Show details on source website

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          "events": [
            {
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            },
            {
              "fixed": "2.1.163"
            }
          ],
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        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-54316"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-183",
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      "CWE-515"
    ],
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  },
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  "modified": "2026-07-20T21:10:30Z",
  "published": "2026-06-17T18:06:06Z",
  "references": [
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    },
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      "url": "https://github.com/anthropics/claude-code"
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  "schema_version": "1.4.0",
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      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
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  "summary": "Claude Code: Out-of-Band Data Exfiltration via Pre-Approved HuggingFace Domain in WebFetch"
}

Mitigation
Implementation

Ensure that all reserved fields are set to zero before messages are sent and that no unnecessary information is included.

No CAPEC attack patterns related to this CWE.