lnd v0.21.6-beta

Release notes

⚠️ Security: CVE-2026-98432 (Linux kernel)

CVE-2026-98432 is a use-after-free in the Linux kernel's IPv4 TCP stack. It is not specific to MPTCP, but the demonstrated remote exploit requires an MPTCP listener, which Go 1.24+ enables by default. This release disables MPTCP listeners in lnd by default, which closes the demonstrated exploit path through lnd. It is a mitigation, not a fix: the kernel patch is the only fix.

Linux operators should:

• Upgrade to this release.

• Disable MPTCP on the host (sudo sysctl -w net.mptcp.enabled=0), since other services on the machine are not covered by this release.

• Install a patched kernel as soon as your distribution ships one.

If you cannot upgrade yet, start your existing binary with the environment variable GODEBUG=multipathtcp=0, which turns off Go's default MPTCP listeners. Do not set GODEBUG=multipathtcp=1 to re-enable MPTCP until your kernel is patched. The Go team's discussion of the issue is at golang/go#82717.

See the release notes for the full instructions, including Docker and firewall guidance. Windows and macOS are not affected.

Database Migrations

There are no migrations in this release.

Verifying the Release

In order to verify the release, you'll need to have gpg or gpg2 installed on your system. Once you've obtained a copy (and hopefully verified that as well), you'll first need to import the keys that have signed this release if you haven't done so already:

curl https://raw.githubusercontent.com/lightningnetwork/lnd/master/scripts/keys/roasbeef.asc | gpg --import

Once you have the required PGP keys, you can verify the release (assuming manifest-roasbeef-v0.21.6-beta.sig and manifest-v0.21.6-beta.txt are in the current directory) with:

gpg --verify manifest-roasbeef-v0.21.6-beta.sig manifest-v0.21.6-beta.txt

You should see the following if the verification was successful:

gpg: Signature made Wed Sep 30 17:35:20 2020 PDT

gpg: using RSA key 60A1FA7DA5BFF08BDCBBE7903BBD59E99B280306

gpg: Good signature from "Olaoluwa Osuntokun <laolu32@gmail.com>" [ultimate]

That will verify the signature of the manifest file, which ensures integrity and authenticity of the archive you've downloaded locally containing the binaries. Next, depending on your operating system, you should then re-compute the sha256 hash of the archive with shasum -a 256 <filename>, compare it with the corresponding one in the manifest file, and ensure they match exactly.

Verifying the Release Timestamp

From this new version onwards, in addition time-stamping the git tag with OpenTimestamps, we'll also now timestamp the manifest file along with its signature. Two new files are now included along with the rest of our release artifacts: manifest-roasbeef-v0.21.6-beta.sig.ots.

Assuming you have the opentimestamps client installed locally, the timestamps can be verified with the following commands:

ots verify manifest-roasbeef-v0.21.6-beta.sig.ots -f manifest-roasbeef-v0.21.6-beta.sig

Alternatively, the OpenTimestamps website can be used to verify timestamps if one doesn't have a bitcoind instance accessible locally.

These timestamps should give users confidence in the integrity of this release even after the key that signed the release expires.

Verifying the Release Binaries

Our release binaries are fully reproducible. Third parties are able to verify that the release binaries were produced properly without having to trust the release manager(s). See our reproducible builds guide for how this can be achieved.

The release binaries are compiled with go1.27.3, which is required by verifiers to arrive at the same ones.

They include the following build tags: autopilotrpc, signrpc, walletrpc, chainrpc, invoicesrpc, neutrinorpc, routerrpc, watchtowerrpc, monitoring, peersrpc, kvdb_postrgres, kvdb_etcd and kvdb_sqlite. Note that these are already included in the release script, so they do not need to be provided.

The make release command can be used to ensure one rebuilds with all the same flags…