Vulnerability-Lookup

CVE-2026-75828 (GCVE-0-2026-75828)

Vulnerability from cvelistv5 – Published: 2026-08-18 11:19 – Updated: 2026-08-18 13:45

Title

Grav before 2.0.15 Stored XSS via detectXss() Quote Bypass

Summary

Grav before 2.0.15 contains a stored cross-site scripting vulnerability in the detectXss() function where unpaired quotes in unquoted attribute values bypass event-handler detection. Authenticated editors can inject event handlers like onerror= that pass validation and execute in visitor browsers when page content is rendered.

Severity

9.3 (Critical)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

8.7 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-18 13:45 UTC

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Assigner

VulnCheck mitre root

References

2 references

URL	Tags
https://github.com/getgrav/grav/security/advisori…	vendor-advisory
https://www.vulncheck.com/advisories/grav-before-…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
getgrav	grav	Affected: 0 , < 2.0.15 (semver) Unaffected: 2.0.15 (semver) cpe:2.3:a:getgrav:grav::::::::

Date Public

2026-08-03 00:00

Credits

arpitjain099

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-75828

Vulnerability from fkie_nvd - Published: 2026-08-18 12:19 - Updated: 2026-09-08 20:32

Severity

8.7 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Summary

References

	URL	Tags
	disclosure@vulncheck.com	https://github.com/getgrav/grav/security/advisories/GHSA-vfmf-q6x9-cw96
	disclosure@vulncheck.com	https://www.vulncheck.com/advisories/grav-before-stored-xss-via-detectxss-quote-bypass
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/getgrav/grav/security/advisories/GHSA-vfmf-q6x9-cw96

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "HIGH",
          "vulnIntegrityImpact": "HIGH",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-75828",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-18T13:45:33.428319Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-18T12:19:32.690",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-vfmf-q6x9-cw96"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://www.vulncheck.com/advisories/grav-before-stored-xss-via-detectxss-quote-bypass"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-vfmf-q6x9-cw96"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Secondary"
    }
  ]
}

GHSA-9PR6-8R9W-WVMJ

Vulnerability from github – Published: 2026-08-18 12:31 – Updated: 2026-09-17 20:43

Withdrawn 2026-09-17

Summary

Duplicate Advisory: Grav: detectXss() misses an event-handler attribute after an unpaired quote in an unquoted attribute value, giving stored XSS

Details

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-vfmf-q6x9-cw96. This link is maintained to preserve external references.

Original Description

Severity

8.7 (High)


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

9.3 (Critical)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c 2.0.15"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "getgrav/grav"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-17T20:43:22Z",
    "nvd_published_at": "2026-08-18T12:19:32Z",
    "severity": "CRITICAL"
  },
  "details": "### Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-vfmf-q6x9-cw96. This link is maintained to preserve external references.\n\n### Original Description\nGrav before 2.0.15 contains a stored cross-site scripting vulnerability in the detectXss() function where unpaired quotes in unquoted attribute values bypass event-handler detection. Authenticated editors can inject event handlers like onerror= that pass validation and execute in visitor browsers when page content is rendered.",
  "id": "GHSA-9pr6-8r9w-wvmj",
  "modified": "2026-09-17T20:43:22Z",
  "published": "2026-08-18T12:31:22Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-vfmf-q6x9-cw96"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-75828"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/grav-before-stored-xss-via-detectxss-quote-bypass"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Duplicate Advisory: Grav: detectXss() misses an event-handler attribute after an unpaired quote in an unquoted attribute value, giving stored XSS",
  "withdrawn": "2026-09-17T20:43:22Z"
}

GHSA-VFMF-Q6X9-CW96

Vulnerability from github – Published: 2026-09-17 20:43 – Updated: 2026-09-17 20:43

Summary

Grav: detectXss() misses an event-handler attribute after an unpaired quote in an unquoted attribute value, giving stored XSS

Details

Affected versions and vulnerable location

Confirmed on grav core at 78ebfc1 (tag 2.0.13).
Detector: system/src/Grav/Common/Security.php:290, the on_events regex, run via patternMatches() (:315-330).
The on_events pattern at HEAD: #<(?:"[^"]*"|'[^']*'|[^>"'])*?(?:[\s\x00-\x20"'/]|"[^"]*"|'[^']*')on\s*[a-z]+\s*=#iu
Sole save-time guard for non-super content: Validation::checkSafety() (system/src/Grav/Common/Data/Validation.php:160 scalars, :165 arrays), invoked per field from BlueprintSchema::validate -> Validation::checkSafety (system/src/Grav/Common/Data/BlueprintSchema.php:248). security.xss_whitelist: [admin.super] exempts only super-admins (Validation.php:148).

Root cause (distinct from GHSA-269c)

GHSA-269c hardened the tag-body scan to be quote-aware so a > inside a paired quoted attribute value is treated as data, not a tag close. That same quote-awareness opened a new gap: the regex treats ANY " or ' as a string delimiter, but HTML only enters a quoted-value state when a quote appears immediately after =. A single unpaired quote sitting inside an unquoted attribute value is, to the browser, just a value character; to the regex it is an unterminated string that neither [^>"'] nor "[^"]*" can consume, so the lazy tag-body scan cannot advance past it to reach the following on...= handler. No alignment matches and detectXss() returns null.

Proof (executed)

The detector was replicated verbatim (the on_events regex plus patternMatches) with the shipped system/config/security.yaml defaults and run under PHP. Observed:

baseline  <img src=x onerror=alert(1)>            => blocked (on_events)
GHSA-269c <img src=x title=">" onerror=alert(1)>  => blocked (on_events)   # prior fix works
BYPASS A  <img src=x" onerror=alert(1)>           => PASSES (no XSS detected)
BYPASS B  <img title=x" onerror=alert(1)>         => PASSES (no XSS detected)
BYPASS C  <a href=x" onmouseover=alert(1)>x</a>   => PASSES (no XSS detected)
BYPASS D  <img src=x' onerror=alert(1)>           => PASSES (no XSS detected)
BYPASS E  <div id=x" onmouseover=alert(1)>hover</div> => PASSES (no XSS detected)

Browser tokenization of <img src=x" onerror=alert(1)>: src takes the unquoted value x" (space ends it), onerror is parsed as a separate live attribute, src 404s and onerror fires. None of the other rules cover it: img/a/div are not in xss_dangerous_tags, there is no javascript:/data: scheme and no style/url/expression.

Reachability

checkSafety() is the only save-time XSS screen for a non-super editor. The pages blueprint validates header.title (type: text) and page content (markdown/textarea) with xss_check on, so a bare onerror= is rejected but the payload above is stored verbatim. Page content is emitted through {{ page.content|raw }} and raw inline HTML passes Parsedown by default (markdown.escape_markup: false), so the handler runs for every visitor. The same detector core also backs Security::detectXssInEditorContent() (the GHSA-2c4f render-time-Twig save gate; callers Page.php:1359, Flex/Types/Pages/PageObject.php:194), the detectXssFromPages() admin scanner (Admin.php:2096), and the xss() Twig function, so all of them report the payload clean.

Auth required: an authenticated content editor with page/form edit rights but WITHOUT admin.super.

Suggested fix

Make the tag-body scan treat a quote as a delimiter only in the after-= position, or normalize unquoted attribute values before the handler scan, so an unpaired quote inside an unquoted value cannot mask a following on...=. A targeted addition: also flag on<name>= sequences that appear after a lone unbalanced quote within the same tag. Because detectXss() is a denylist, consider additionally encoding "/' in stored non-super content, or defaulting markdown.escape_markup: true for non-super authors.

Severity and CVSS reasoning

Suggested severity: High (matches GHSA-269c and the other stored-XSS advisories in this codebase).

Suggested CVSS:3.1 vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N (8.7).

PR:L: a non-super editor account.
UI:R: a visitor renders the page (for onerror the image simply loads/fails automatically).
S:C/C:H/I:H: script in the site origin against every visitor, including admins viewing the content.

How I found it and a note on tooling

I read detectXss() and reasoned about the difference between the HTML tokenizer's quoted-value state and the regex's string handling, then replicated the exact on_events pattern and patternMatches() with the shipped default config and ran the payloads to confirm the bypass and that the GHSA-269c payload is still blocked. I used AI assistance for the analysis and drafting and verified the detector behavior by execution. This is executed against a faithful replica of the detector with production config, not against a full running Grav site.

Severity

8.7 (High)


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

9.3 (Critical)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.0.14"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "getgrav/grav"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.0.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-75828"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-17T20:43:43Z",
    "nvd_published_at": null,
    "severity": "CRITICAL"
  },
  "details": "## Affected versions and vulnerable location\n\n- Confirmed on grav core at `78ebfc1` (tag 2.0.13).\n- Detector: `system/src/Grav/Common/Security.php:290`, the `on_events` regex, run via `patternMatches()` (`:315-330`).\n- The `on_events` pattern at HEAD:\n  `#\u003c(?:\"[^\"]*\"|\u0027[^\u0027]*\u0027|[^\u003e\"\u0027])*?(?:[\\s\\x00-\\x20\"\u0027/]|\"[^\"]*\"|\u0027[^\u0027]*\u0027)on\\s*[a-z]+\\s*=#iu`\n- Sole save-time guard for non-super content: `Validation::checkSafety()` (`system/src/Grav/Common/Data/Validation.php:160` scalars, `:165` arrays), invoked per field from `BlueprintSchema::validate` -\u003e `Validation::checkSafety` (`system/src/Grav/Common/Data/BlueprintSchema.php:248`). `security.xss_whitelist: [admin.super]` exempts only super-admins (`Validation.php:148`).\n\n## Root cause (distinct from GHSA-269c)\n\nGHSA-269c hardened the tag-body scan to be quote-aware so a `\u003e` inside a paired quoted attribute value is treated as data, not a tag close. That same quote-awareness opened a new gap: the regex treats ANY `\"` or `\u0027` as a string delimiter, but HTML only enters a quoted-value state when a quote appears immediately after `=`. A single unpaired quote sitting inside an unquoted attribute value is, to the browser, just a value character; to the regex it is an unterminated string that neither `[^\u003e\"\u0027]` nor `\"[^\"]*\"` can consume, so the lazy tag-body scan cannot advance past it to reach the following ` on...=` handler. No alignment matches and `detectXss()` returns null.\n\n## Proof (executed)\n\nThe detector was replicated verbatim (the `on_events` regex plus `patternMatches`) with the shipped `system/config/security.yaml` defaults and run under PHP. Observed:\n\n```text\nbaseline  \u003cimg src=x onerror=alert(1)\u003e            =\u003e blocked (on_events)\nGHSA-269c \u003cimg src=x title=\"\u003e\" onerror=alert(1)\u003e  =\u003e blocked (on_events)   # prior fix works\nBYPASS A  \u003cimg src=x\" onerror=alert(1)\u003e           =\u003e PASSES (no XSS detected)\nBYPASS B  \u003cimg title=x\" onerror=alert(1)\u003e         =\u003e PASSES (no XSS detected)\nBYPASS C  \u003ca href=x\" onmouseover=alert(1)\u003ex\u003c/a\u003e   =\u003e PASSES (no XSS detected)\nBYPASS D  \u003cimg src=x\u0027 onerror=alert(1)\u003e           =\u003e PASSES (no XSS detected)\nBYPASS E  \u003cdiv id=x\" onmouseover=alert(1)\u003ehover\u003c/div\u003e =\u003e PASSES (no XSS detected)\n```\n\nBrowser tokenization of `\u003cimg src=x\" onerror=alert(1)\u003e`: `src` takes the unquoted value `x\"` (space ends it), `onerror` is parsed as a separate live attribute, `src` 404s and `onerror` fires. None of the other rules cover it: `img`/`a`/`div` are not in `xss_dangerous_tags`, there is no `javascript:`/`data:` scheme and no `style`/`url`/`expression`.\n\n## Reachability\n\n`checkSafety()` is the only save-time XSS screen for a non-super editor. The pages blueprint validates `header.title` (`type: text`) and page `content` (markdown/textarea) with `xss_check` on, so a bare `onerror=` is rejected but the payload above is stored verbatim. Page content is emitted through `{{ page.content|raw }}` and raw inline HTML passes Parsedown by default (`markdown.escape_markup: false`), so the handler runs for every visitor. The same detector core also backs `Security::detectXssInEditorContent()` (the GHSA-2c4f render-time-Twig save gate; callers `Page.php:1359`, `Flex/Types/Pages/PageObject.php:194`), the `detectXssFromPages()` admin scanner (`Admin.php:2096`), and the `xss()` Twig function, so all of them report the payload clean.\n\nAuth required: an authenticated content editor with page/form edit rights but WITHOUT `admin.super`.\n\n## Suggested fix\n\nMake the tag-body scan treat a quote as a delimiter only in the after-`=` position, or normalize unquoted attribute values before the handler scan, so an unpaired quote inside an unquoted value cannot mask a following `on...=`. A targeted addition: also flag ` on\u003cname\u003e=` sequences that appear after a lone unbalanced quote within the same tag. Because `detectXss()` is a denylist, consider additionally encoding `\"`/`\u0027` in stored non-super content, or defaulting `markdown.escape_markup: true` for non-super authors.\n\n## Severity and CVSS reasoning\n\nSuggested severity: High (matches GHSA-269c and the other stored-XSS advisories in this codebase).\n\nSuggested CVSS:3.1 vector: `CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N` (8.7).\n\n- `PR:L`: a non-super editor account.\n- `UI:R`: a visitor renders the page (for `onerror` the image simply loads/fails automatically).\n- `S:C/C:H/I:H`: script in the site origin against every visitor, including admins viewing the content.\n\n## How I found it and a note on tooling\n\nI read `detectXss()` and reasoned about the difference between the HTML tokenizer\u0027s quoted-value state and the regex\u0027s string handling, then replicated the exact `on_events` pattern and `patternMatches()` with the shipped default config and ran the payloads to confirm the bypass and that the GHSA-269c payload is still blocked. I used AI assistance for the analysis and drafting and verified the detector behavior by execution. This is executed against a faithful replica of the detector with production config, not against a full running Grav site.",
  "id": "GHSA-vfmf-q6x9-cw96",
  "modified": "2026-09-17T20:43:43Z",
  "published": "2026-09-17T20:43:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-vfmf-q6x9-cw96"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-75828"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/getgrav/grav"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/grav-before-stored-xss-via-detectxss-quote-bypass"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Grav: detectXss() misses an event-handler attribute after an unpaired quote in an unquoted attribute value, giving stored XSS"
}

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.

Detection rules are retrieved from Rulezet.

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.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-75828 (GCVE-0-2026-75828)

FKIE_CVE-2026-75828

GHSA-9PR6-8R9W-WVMJ

Duplicate Advisory

Original Description

GHSA-VFMF-Q6X9-CW96

Affected versions and vulnerable location

Root cause (distinct from GHSA-269c)

Proof (executed)

Reachability

Suggested fix

Severity and CVSS reasoning

How I found it and a note on tooling

Tags

Sightings

Nomenclature

Related by attack behaviour