A flaw was found in the HTTP/2 protocol implementation within the Go standard library (golang.org/x/net and net/http/internal/http2). A remote attacker can exploit this vulnerability by sending a specially crafted HTTP/2 SETTINGS frame with the SETTINGS_MAX_FRAME_SIZE parameter set to zero. This malicious frame causes the transport layer to enter an infinite loop of writing CONTINUATION frames, leading to resource exhaustion and a Denial of Service (DoS) condition.

The insights-runtime-extractor runs as a privileged DaemonSet (`hostPID: true`) that scans container processes for runtime fingerprinting. When scanning a container, the coordinator: 1. **fork()s** a child process 2. **setns()** into the target container's PID and mount namespaces 3. **fchdir()** back to an orphaned FD pointing at the extractor's own root filesystem (where `/crio.sock` is hostPath-mounted) 4. Calls **only `seteuid(target_uid)`** — changing the effective UID but leaving the **real UID and saved-set-UID at 0** and **retaining the permitted capability set** 5. The `check_no_privileged_perms()` guard inspects only the Effective capability set (so it passes), and is **skipped entirely when the target runs as uid 0** 6. The `VersionExecutable` fingerprint invokes `fpr_kind_executable` with `process.command_line[0]` — the target's argv[0], read from `/proc/<pid>/cmdline` and **fully controlled by the workload** 7. `fpr_kind_executable` calls `exec.Command(executable, "--version").Output()` — executing the **workload's own binary** inside the workload's mount namespace while **ruid=0 in the host user namespace** The executed process can call `setuid(0)` to restore full root with `CAP_SYS_ADMIN`, and inherits the orphaned cwd which resolves into the extractor container's filesystem containing the host CRI-O socket. ## Affected Code ### 1. Insufficient privilege drop (Rust — extractor coordinator) **File:** `extractor/src/insights_runtime_extractor.rs` ```rust // Lines 139-146 — seteuid-only drop, guard skipped for root containers join_process_namespaces(process.pid)?; change_dir(current_dir); switch_user(*process.uid)?; if *process.uid != 0 { perms::check_no_privileged_perms() .expect("Must not have privileged permissions to run fingerprints"); } fingerprint::run_fingerprints(&config, out_dir, &process); ``` ```rust // Lines 182-185 — only effective UID changed; ruid/suid stay 0 fn switch_user(uid: u32) -> Result<(), ScannerError> { debug!("... Becoming user: {uid}"); seteuid(uid.into()).map_err(|e| ScannerError::Errno(e)) } ``` ### 2. Execution of untrusted binary (Go — fingerprint) **File:** `fingerprints/pkg/utils/file.go` ```go // Lines 75-80 — executes a path taken verbatim from workload's argv[0] func GetExecutableVersionOutput(executable string) (string, error) { out, err := exec.Command(executable, "--version").Output() if err != nil { return "", err } return string(out), nil } ``` ### 3. Workload-controlled path forwarded (Rust — version_executable) **File:** `version_executable.rs` ```rust // Lines 29-34 — workload-controlled command_line[0] forwarded to fingerprint return Some(vec![ fpr_kind_executable, out_dir.to_string(), String::from(&process.command_line[0]), String::from(&version_executable.runtime_kind_name), ]); ``` ## Attack Pattern **Attacker:** Any tenant able to schedule a pod (unprivileged, any namespace) **Victim:** The node running the insights-runtime-extractor DaemonSet **Trigger:** Automatic — the DaemonSet scans all container processes on the node **Attack sequence:** 1. Attacker creates a pod whose process name matches a configured versioned-executable pattern (`node`, `python`, `python3`, `MainThread`, or contains `java`) 2. The pod's main binary (at the path matching argv[0]) is a malicious executable that calls `setuid(0)` to restore root 3. When the insights operator triggers a scan, the DaemonSet forks, enters the attacker's mount namespace, and executes the attacker's binary with ruid=0 4. The attacker's code regains full root with `CAP_SYS_ADMIN` in the host user namespace 5. The inherited cwd contains the host CRI-O socket → full node compromise