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Fencer Intel
high 7.7

CVE-2026-115539 json

Cluster-API proxy overwrites forwarded client identity with its own

published yesterday modified yesterday also EUVD-2026-122880 , GHSA-628g-hv7f-pgjc

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository moby/swarmkit. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
7.7
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 11%
public exploits
0
none known

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.

Patch / fix

  • moby SwarmKit 2.1.3
  • docker Alpine 3.24 29.9.3-r0

alpine advisories ALPINE-CVE-2026-115539

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Is CVE-2026-115539 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Exploit prediction

0.21% chance of exploitation in the next 30 days, higher than 11% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 7.7 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 7.7 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • moby SwarmKit
  • Docker Docker Engine
  • moby Moby

Classification

Weakness
  • CWE-441 Unintended Proxy or Intermediary
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of moby/swarmkit published their own advisory on GitHub. Reviewed sources take precedence over it.