SSRF in sliver teamserver

Exploitation

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

CVSS 4.0

6.9 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N · score source

EPSS

• CVE-2025-27090: 0.63% estimated exploitation activity in the next 30 days; percentile 50.32 (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 The reverse port forwarding in sliver teamserver allows the implant to open a reverse tunnel on the sliver teamserver without verifying if the operator instructed the implant to do so Reproduction steps Run server Generate binary Run it on windows, then Task manager - find process - Create memory dump file Install RogueSliver and get the certs Start callback listener. Teamserver will connect when POC is run and send "ssrf poc" to nc Run the poc (pasted at bottom of this file) Details We see here an envelope is read from the connection and if the envelope.Type matches a handler the handler will be executed The available handlers: If we send an envelope with the envelope.Type equaling MsgTunnelData, we will enter the tunnelDataHandler function The createReverseTunnelHandler reads the envelope, creating a socket for req.Rportfwd.Host and req.Rportfwd.Port. It will write recv.Data to it Impact For current POC, mostly just leaking teamserver origin IP behind redirectors. I am 99%…

Published by the source

19 Feb 2025, 21:11 UTC

Last modified by the source

20 Feb 2025, 22:47 UTC

Source last checked

26 Oct 2026, 15:08 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fh4v-v779-4g2w

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# Patch Next advisory brief: CVE-2025-27090

Advisory: SSRF in sliver teamserver
IDs: CVE-2025-27090, GHSA-fh4v-v779-4g2w
Record: https://patchnext.com/advisories/cve-2025-27090 (revision 1, source checked 26 Oct 2026, 15:08 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/bishopfox/sliver 1.5.43. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/bishopfox/sliver: affected >= 1.5.26, <= 1.5.42; fixed in 1.5.43

## Suggested inspection (read-only)
- Go github.com/bishopfox/sliver: 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/bishopfox/sliver.
- 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-fh4v-v779-4g2w (GitHub-reviewed advisory GHSA-fh4v-v779-4g2w lists affected ranges: Go github.com/bishopfox/sliver >=1.5.26 <=1.5.42)

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