Cluster-API proxy overwrites forwarded client identity with its own
- Exploited
- No known exploitation
- Fix
- Fixed in 2.1.3
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 2.1.3.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 28/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
SwarmKit's Cluster-API proxy can overwrite a forwarded client's TLS identity with an intermediary manager's identity. WithMetadataForwardTLSInfo replaces outgoing metadata with a copy of the incoming metadata, discarding the redirect guard's changes when built with grpc-go 1.39 or later. During a short window after a leader change, two proxy hops through managers with inconsistent views of the leader can allow an attacker possessing a valid worker node TLS certificate and private key to obtain a manager node certificate for the attacker's own key, escalating privileges from worker to manager. Applications built with an affected SwarmKit version and grpc-go 1.39 or later are impacted.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure3/25Reachable over the network · Unknown: No advisory context yet
- Reach17/20Affects Docker (a widely deployed server, runtime, framework or database)
- Severity7.7/10CVSS 7.7
- No patch0/5No signal
What would change the score
- Would score about 83 if added to CISA KEV
- Would score about 78 if CISA's SSVC rates exploitation active
- Would score about 47 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 2.1.3.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-115539 (Cluster-API proxy overwrites forwarded client identity with its own), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-115539 (entry last updated 2026-11-10): Affected: - moby SwarmKit: fixed in 2.1.3 - Docker Docker Engine: from 23.0.0 - moby Moby: through 2.0.0-beta.28 - moby SwarmKit: from 1.12.1-0.20220307221335-616e8db4c3b0 Fixed versions: 2.1.3. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-115539 is not listed as of cve.now's last read. This KEV status is for CVE-2026-115539 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/moby/swarmkit/security/advisories/GHSA-628g-hv7f-pgjc Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-115539 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-115539.
Timeline
- CVE published
- First seen by cve.now
- Posted on X by cve.now
Affected versions
- github.com/moby/swarmkit/v2
fixed in 2.1.3
- github.com/docker/docker
From 23.0.0
- github.com/moby/moby/v2
through 2.0.0-beta.28
- github.com/moby/swarmkit
From 1.12.1-0.20220307221335-616e8db4c3b0
Evidence 3
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
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Questions about CVE-2026-115539
Is CVE-2026-115539 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: cve.now feed data
Which versions are affected by CVE-2026-115539?
github.com/moby/swarmkit/v2: before 2.1.3. github.com/docker/docker: from 23.0.0. github.com/moby/moby/v2: through 2.0.0-beta.28. github.com/moby/swarmkit: from 1.12.1-0.20220307221335-616e8db4c3b0.Source: cve.now feed data
How do I fix CVE-2026-115539?
Upgrade to a fixed version: 2.1.3.Source: cve.now feed data