Vulnerability-Lookup

CVE-2026-45695 (GCVE-0-2026-45695)

Vulnerability from cvelistv5 – Published: 2026-07-16 15:42 – Updated: 2026-07-16 18:08

Previdian

Title

Kopia: Unauthenticated RCE via SSH ProxyCommand Injection when --insecure --without-password is used

Summary

Kopia is a cross-platform backup tool for Windows, macOS, and Linux with fast incremental backups, client-side end-to-end encryption, compression, and data deduplication. Prior to 0.23.0, Kopia's HTTP server started with --without-password accepts unauthenticated requests to /api/v1/repo/exists and forwards attacker-supplied SFTP storage configuration to blob.NewStorage, where externalSSH: true and sshArguments containing -oProxyCommand=<cmd> can cause exec.CommandContext("ssh") to invoke the command through OpenSSH. This issue is fixed in version 0.23.0.

Severity

9.8 (Critical)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-16 18:06 UTC

CWE

CWE-78 - Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
CWE-306 - Missing Authentication for Critical Function

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/kopia/kopia/security/advisorie…	x_refsource_CONFIRM
https://github.com/kopia/kopia/pull/5354	x_refsource_MISC
https://github.com/kopia/kopia/commit/c26c6a1b973…	x_refsource_MISC
https://github.com/kopia/kopia/releases/tag/v0.23.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
kopia	kopia	Affected: < 0.23.0	guessed

Previdian

Known Exploited Vulnerability - GCVE BCP-07 Compliant

KEV entry ID: 7ae70118-bb20-4e14-a01c-cfb2d14d7491

Vulnerability ID: CVE-2026-45695

Status: Confirmed

Status Updated: 2026-09-10 00:00 UTC

Exploited: Yes

Timestamps

First Seen: 2026-09-10

Asserted: 2026-09-10

Scope

Evidence

Type: Public Report

Signal: Successful Exploitation

Confidence: 70%

Source: previdian

Details

Feed	Previdian (previdian.com)
Title	Kopia: Unauthenticated RCE via SSH ProxyCommand Injection when --insecure --without-password is used
Cve Id	CVE-2026-45695
Vendor	Kopia
Ghsa Id	None
Product	kopia
Added Date	2026-09-10T00:00:00.000Z
Cvss Score	9.8
Epss Score	0.0161
Previous Ids
Cvss Severity	CRITICAL
Virtual Patch	False
Cvss Estimated	False
Epss Percentile	0.74492
Used In Malware	unknown
Vulnerability Id	CVE-2026-45695
Ahead Of Cisa Kev	None
Not Yet In Cisa Kev	True

References

Created: 2026-09-11 11:00 UTC | Updated: 2026-09-11 11:00 UTC

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-45695

Vulnerability from fkie_nvd - Published: 2026-07-16 16:19 - Updated: 2026-07-16 19:16

Previdian

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/kopia/kopia/commit/c26c6a1b9734c5089217986ffa5cd19f8a6b8900
	security-advisories@github.com	https://github.com/kopia/kopia/pull/5354
	security-advisories@github.com	https://github.com/kopia/kopia/releases/tag/v0.23.0
	security-advisories@github.com	https://github.com/kopia/kopia/security/advisories/GHSA-2q4c-3mrw-63c3

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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}

GHSA-2Q4C-3MRW-63C3

Vulnerability from github – Published: 2026-05-19 19:18 – Updated: 2026-05-19 19:18

Summary

Kopia: RCE via SSH ProxyCommand Injection

Details

Summary

Kopia's HTTP server, when started with --without-password, accepts unauthenticated requests to /api/v1/repo/exists. The handler forwards an attacker-supplied storage configuration to blob.NewStorage. For SFTP backends with externalSSH: true, that path constructs a process command line by splitting sshArguments on spaces and passes the result directly to exec.CommandContext("ssh"). An -oProxyCommand=<cmd> token in sshArguments causes OpenSSH to invoke <cmd> via $SHELL -c before any TCP connection is attempted, giving the requester arbitrary command execution as the Kopia process user.

Analysis

internal/server/server_authz_checks.go lines 61–73:

when the server is started without --server-username or --server-password, getAuthenticator() returns nil and requireUIUser unconditionally authorizes the request. Every endpoint registered through handleUIPossiblyNotConnected becomes accessible without credentials.

repo/blob/sftp/sftp_storage.go lines 448–468:

opt.SSHArguments is populated from the JSON request body (storage.config.sshArguments). The string is split only on the literal ASCII space character, there is no shell style tokenizer, no quote handling, and no allowlist. Whatever tokens the caller supplies are appended to the ssh argv.

OpenSSH treats -oProxyCommand=<value> as a directive to execute <value> via the user's shell ($SHELL -c <value>) and pipe the SSH transport over its stdio. The shell invocation happens before SSH attempts a TCP connection, so the command runs even when the target host is unreachable.

Impact

No user interaction is required. No valid credentials are required. The exploit is a single HTTP request.

Credits

This vulnerability was discovered and responsibly disclosed by Daniele Berardinelli.

Mitigation

https://github.com/kopia/kopia/pull/5354 disallows starting of a server without a password which also listens on a non-loopback interface.

Severity

9.8 (Critical)


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

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.22.3"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/kopia/kopia"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45695"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-306",
      "CWE-78"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-19T19:18:32Z",
    "nvd_published_at": null,
    "severity": "CRITICAL"
  },
  "details": "## Summary\n\nKopia\u0027s HTTP server, when started with `--without-password `, accepts unauthenticated requests to `/api/v1/repo/exists`. The handler forwards an attacker-supplied storage configuration to `blob.NewStorage`. For SFTP backends with `externalSSH: true`, that path constructs a process command line by splitting `sshArguments` on spaces and passes the result directly to `exec.CommandContext(\"ssh\")`. An `-oProxyCommand=\u003ccmd\u003e` token in `sshArguments` causes OpenSSH to invoke `\u003ccmd\u003e` via `$SHELL -c` before any TCP connection is attempted, giving the requester arbitrary command execution as the Kopia process user.\n\n## Analysis\n\n[`internal/server/server_authz_checks.go` lines 61\u201373](https://github.com/kopia/kopia/blob/v0.22.3/internal/server/server_authz_checks.go#L61-L73):\n\nwhen the server is started without `--server-username` or `--server-password`, `getAuthenticator()` returns `nil` and `requireUIUser` unconditionally authorizes the request. Every endpoint registered through `handleUIPossiblyNotConnected` becomes accessible without credentials.\n\n[`repo/blob/sftp/sftp_storage.go` lines 448\u2013468](https://github.com/kopia/kopia/blob/v0.22.3/repo/blob/sftp/sftp_storage.go#L448-L468):\n\n`opt.SSHArguments` is populated from the JSON request body (`storage.config.sshArguments`). The string is split only on the literal ASCII space character, there is no shell style tokenizer, no quote handling, and no allowlist. Whatever tokens the caller supplies are appended to the `ssh` argv. \n\nOpenSSH treats `-oProxyCommand=\u003cvalue\u003e` as a directive to execute `\u003cvalue\u003e` via the user\u0027s shell (`$SHELL -c \u003cvalue\u003e`) and pipe the SSH transport over its stdio. The shell invocation happens before SSH attempts a TCP connection, so the command runs even when the target host is unreachable.\n\n## Impact\n\nNo user interaction is required. No valid credentials are required. The exploit is a single HTTP request.\n\n## Credits \n\nThis vulnerability was discovered and responsibly disclosed by Daniele Berardinelli.\n\n## Mitigation\nhttps://github.com/kopia/kopia/pull/5354 disallows starting of a server without a password which also listens on a non-loopback interface.",
  "id": "GHSA-2q4c-3mrw-63c3",
  "modified": "2026-05-19T19:18:32Z",
  "published": "2026-05-19T19:18:32Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/kopia/kopia/security/advisories/GHSA-2q4c-3mrw-63c3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/kopia/kopia/pull/5354"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/kopia/kopia"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Kopia: RCE via SSH ProxyCommand Injection"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-45695 (GCVE-0-2026-45695)

Previdian

Known Exploited Vulnerability - GCVE BCP-07 Compliant

Timestamps

Scope

Evidence

Public Report Successful Exploitation Confidence: 70% Source: previdian

Details

References

FKIE_CVE-2026-45695

GHSA-2Q4C-3MRW-63C3

Summary

Analysis

Impact

Credits

Mitigation

Tags

Sightings

Nomenclature

Related by attack behaviour