Removed: unprivileged access to most AF_ALG algorithms, and off-CPU accelerator support, which an earlier commit in the same cycle dropped outright.
Outcome: AF_ALG became restrictive by default in the mainline kernel — unprivileged callers keep an allowlist of algorithms, privileged callers a slightly longer one — with crypto.af_alg_restrict available to widen it or switch the interface off entirely.
A June 2026 commit in the mainline kernel restricted AF_ALG, the interface that lets userspace processes call the kernel’s crypto code, by default. Eric Biggers’ commit message is blunter than most kernel prose: AF_ALG “is a frequent source of vulnerabilities and a maintenance nightmare” and “exposes far more functionality to userspace than ever should have been exposed, especially to unprivileged processes.” The new crypto.af_alg_restrict sysctl defaults to 1, which limits unprivileged callers to an allowlist of algorithms and gives privileged callers a slightly longer one; setting it to 2 turns the interface off entirely. An earlier commit in the same cycle removed off-CPU accelerator support, citing “huge overheads, both in performance and attack surface.” The maintainers could have kept patching. Instead they narrowed what the interface will do for callers who are not already privileged — the same choice an application team faces with an endpoint only three customers call.
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