Kopia: RCE via SSH ProxyCommand Injection

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-45695: 1.61% estimated exploitation activity in the next 30 days; percentile 75.97 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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/serverauthzchecks.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/sftpstorage.go lines 448–468: opt.SSHArguments is populated…

Published by the source

19 May 2026, 19:18 UTC

Last modified by the source

19 May 2026, 19:18 UTC

Source last checked

26 Oct 2026, 15:22 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2q4c-3mrw-63c3

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# Patch Next advisory brief: CVE-2026-45695

Advisory: Kopia: RCE via SSH ProxyCommand Injection
IDs: CVE-2026-45695, GHSA-2q4c-3mrw-63c3
Record: https://patchnext.com/advisories/cve-2026-45695 (revision 1, source checked 26 Oct 2026, 15:22 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/kopia/kopia 0.23.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/kopia/kopia: affected <= 0.22.3; fixed in 0.23.0

## Suggested inspection (read-only)
- Go github.com/kopia/kopia: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/kopia/kopia.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2q4c-3mrw-63c3 (GitHub-reviewed advisory GHSA-2q4c-3mrw-63c3 lists affected ranges: Go github.com/kopia/kopia >=0 <=0.22.3)

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