Coraza: Native audit-log format allows CRLF injection and log forgery via request body and header fieldsCVE-2026-41504

## Root Cause File: `internal/auditlog/formats.go` — multiple sites write attacker-influenced bytes into the Native audit-log stream without escaping `\r` or `\n`: ```go // Part B — request headers (lines 72–80) for k, vv := range al.Transaction().Request().Headers() { for _, v := range vv { res.WriteByte('\n') res.WriteString(k) res.WriteString(": ") res.WriteString(v) // ← raw } } // Part C — request body (lines 85–86) if body := al.Transaction().Request().Body(); body != "" { res.WriteString(body) // ← raw res.WriteByte('\n') } // Part E — response body (lines 93–94) raw // Part F — response headers (lines 111–118) raw // Part H — error messages (line 125) raw // Part K — matched-rule raw data (line 151) raw ``` The Native format's section structure is line-based: sections are delimited by lines of the form `--<10-char-random-prefix>-<Part>--`, and line-based log parsers / SIEM rules rely on that structure. Any attacker-controlled bytes containing `\n` break the structural invariant and allow the attacker to inject lines that look like genuine audit content. The other two Native-format implementations in Coraza are not affected: the JSON formatter (`formats_json.go`) and the OCSF formatter both round-trip values through `json.Marshal`, which escapes `\r` and `\n`. ## Impact An attacker who can land bytes into any of the listed audit-log fields can inject arbitrary lines — including lines that visually resemble new log entries — into the audit log file of a defender running the default `SecAuditLogFormat Native` configuration. Realistic consequences: - **Forging entries to shift attribution.** An injected line such as `[client "9.9.9.9"] Coraza: Warning. ...` sits alongside genuine matches in Part H, and a human operator (or simple SIEM rule) reading the log cannot tell them apart. - **Confusing SIEM correlation.** Any ingestion pipeline that splits on `--...-[A-Z]--` boundaries or on `[client "..."]` patterns without validating the session prefix will treat the forged lines as separate records. - **Breaking log-parsing tooling.** Grep/awk pipelines, log tailers, and log-rotation tools with line-based assumptions can be poisoned with crafted binary sequences. - **Hiding genuine incidents.** An attacker who can also trigger a rule match on the same transaction (trivial — send any request that matches *any* audit-logged rule) can bury the real match under noise they control. The forged lines cannot trivially impersonate an entire *separate* session: the 10-char random prefix in the real boundaries (`boundaryPrefix := "--" + utils.RandomString(10) + "-"`, line 42) is not predictable from outside, and each transaction uses a fresh prefix. But the integrity of a *single* record is fully compromised, which is enough for the SIEM-confusion and attribution-shifting attacks. ## Proof of Concept Server with `coraza.conf-recommended`-style defaults: ```conf SecRuleEngine On SecAuditEngine On SecAuditLogParts ABCFHZ SecAuditLogType Serial SecAuditLog /tmp/audit.log SecAuditLogFormat Native SecRequestBodyAccess On SecRule REQUEST_METHOD "@rx ." \ "id:1001,phase:1,pass,log,auditlog,msg:'trigger'" ``` ### Body vector — reachable via stock `coraza/v3/http` + `net/http` Send an ordinary urlencoded POST whose body contains raw CRLF sequences and forged boundaries: ``` POST / HTTP/1.1 Content-Type: application/x-www-form-urlencoded evil=benign\r\n--coraza-forged-X--\r\nForgedLine: yes\r\n--coraza-forged-H--\r\n[client "9.9.9.9"] FAKE ATTACK ENTRY ``` Resulting audit.log: ``` --heLNtylvjY-C-- evil=benign --coraza-forged-X-- ForgedLine: yes --coraza-forged-H-- [client "9.9.9.9"] FAKE ATTACK ENTRY --heLNtylvjY-F-- ``` The forged `--coraza-forged-X--` / `--coraza-forged-H--` boundaries and the spoofed `[client "9.9.9.9"]` line are structurally indistinguishable from the surrounding genuine log content. No rule fires, no error is raised, the attack is invisible to the WAF. ### Header vector — reachable via non-net/http integrations only The same effect applies to Part B (request headers) and Part F (response headers) when a header value contains raw `\r\n`. Go's `net/http` rejects such headers at parse time (`400 Bad Request`), so the stock HTTP wrapper is safe from this path; the vector is reachable when Coraza is called with header values that were not validated by `net/http`: - `coraza-spoa` (HAProxy SPOP agent) forwards headers from HAProxy, which has more permissive validation. - `coraza-proxy-wasm` / Envoy WASM hosts forward header values from the upstream proxy. - Custom FFI/WASM hosts and any embedder calling `tx.AddRequestHeader(k, v)` with unvalidated bytes. Other raw-write sites (Part E response body, Part H error messages, Part K matched-rule data) share the same class of issue and should be fixed together. ## Mitigation Escape `\r` and `\n` at every raw-write site in `internal/auditlog/formats.go`. A single package-level helper is sufficient: ```go var logEscaper = strings.NewReplacer("\r", "\\r", "\n", "\\n") // Part B — header values: res.WriteString(logEscaper.Replace(v)) // Part F — header values: same // Part H — error messages: res.WriteString(logEscaper.Replace(alWithErrMsg.ErrorMessage())) // Part K — matched-rule raw data: res.WriteString(logEscaper.Replace(alEntry.Data().Raw())) ``` For Part C / Part E (bodies), the choice is policy-dependent: - **Escape inline** (`logEscaper.Replace(body)`): keeps the log human-readable for text bodies but loses fidelity for binary. - **Base64 / hex-encode** the whole part: binary-safe, matches the spirit of ModSecurity v2's binary-log handling, but less human-readable. Escaping is the minimum; base64 for bodies is the more conservative default and is a reasonable audit-log-default change. ### Additional defensive measure Consider lengthening the `boundaryPrefix` random suffix from 10 chars to ≥16 chars (line 42). This strictly raises the bar for attackers attempting to *fully* forge a separate-looking session (not just inject lines into the current one). Low-cost change; narrows future variants of this bug class. ## Affected versions The Native formatter has been present since `v3.0.0` (file existed at the first-release commit). All releases `>= 3.0.0, <= 3.7.0` are affected when `SecAuditLogFormat Native` is used with `SecAuditLogType Serial` or `SecAuditLogType Concurrent`. **Unaffected:** - Deployments using `SecAuditLogFormat JSON` (`formats_json.go` uses `json.Marshal` which escapes `\r\n`). - Deployments using OCSF output. - Deployments with `SecAuditEngine Off`. ## References - `internal/auditlog/formats.go` lines 42, 72–80 (Part B), 85–88 (Part C), 93–96 (Part E), 111–118 (Part F), 125 (Part H), 151 (Part K) - `coraza.conf-recommended` — default `SecAuditLogFormat Native`, `SecAuditLogParts ABIJDEFHZ` / `ABCFHZ` variants - CWE-117 — Improper Output Neutralization for Logs - CWE-93 — CRLF Injection

Quoted source text, attributed separately from HOL analysis.