# The language-security audit, solved at the root

> On main since rc2: The language-security audit, solved at the root.

Source: https://kern-lang.eu/releases/language-security-audit

On main since rc2

## Release notes

Five independent audits of the language itself were folded into one ranked register (`docs/design/language-security-hardening-2026-08.md`), which first records what holds up (the per-commit Trusting-Trust chain, the Coq-checked E0404 confinement, container isolation that exceeds a default Docker profile, complete overflow checking) and then the holes in the flagship claims, traced to four root causes and fixed at that level rather than per symptom.

### Containment

The seccomp seal denied `socket`/`openat`/`execve` by syscall number, but an `io_uring` ring could issue the same operations without the syscall entry; `io_uring_setup/enter/register` are now denied unconditionally under the seal and in containers. `Cap<Net>` egress narrowing was advisory; `KERN_NET_ALLOW` is now enforced at the C connect leaf, so even an RCE is bounded. Forwarder revocation was decorative (no use path); `forwarder_use_*` now fails closed, the alive flag is atomic, and a new compile error **E0406** forbids an extracted capability from escaping its frame (return, field store, module global, spawn capture), so revocation gates the lifetime, not just the extraction event.

### Taint

Enforcement was per-site code that each forgot a different tag; it is now one env-aware predicate routed through every boundary, string interpolation parts included, and it recurses into struct and union fields, so serialising a struct with a `PersonalData` field to a log or a DB row no longer launders the tag.

### Codegen

Integer `/` and `%` trap on a zero divisor and `INT64_MIN / -1` instead of LLVM undefined behaviour.

### Stdlib

Fallible crypto returns `Result<str>` rather than an in-band `"ERROR:"` string or an empty key, `Untrusted` discharges only into structured sinks (argv, params, auto-escaped templates) with the string escapers gone, CSV cells are quoted against formula injection, and the audit and revocation-feed chains are keyed to the box anchor.

### Trust

A seed-faithfulness CI gate re-derives the seed IR with `kern_v4` and byte-compares it to the manifest, stated as trusting `kern_v4` (a consistently poisoned seed pair would still pass; that is what the independent bootstrap and DDC gates are for). Every fix is box-verified and pinned by a negative test; the register keeps the honest T-model status alongside: flow soundness remains test-backed rather than machine-checked, and the external audit is a business decision not yet taken.