Vulnerability-Lookup

CVE-2026-112921 (GCVE-0-2026-112921)

Vulnerability from cvelistv5 – Published: 2026-10-21 21:37 – Updated: 2026-10-22 00:16

Title

Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request

Summary

Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request. Each Robots::Validate object holds one pure-Perl Aho-Corasick search machine and feeds every User-Agent into it without resetting its state. A User-Agent that ends part-way through a robot name leaves the machine mid-match, so the next User-Agent checked by the same object can complete that name. That client's address is then checked against the robot's DNS rule, which it fails. A remote client can use this to make a site that blocks bad robots block other visitors where the prefix User-Agent string is a suffix of a robot being validated. Note that deployments with Algorithm::AhoCorasick::XS are also affected, since it was unused due to a different bug.

Severity

No CVSS data available.

CWE

CWE-488 - Exposure of Data Element to Wrong Session

Assigner

CPANSec CNA under the redhat root

CNA scorecard C 63/100 over 300 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/robrwo/Robots-Validate/commit/…	patch
https://metacpan.org/release/RRWO/Robots-Validate…	release-notes
https://metacpan.org/release/RRWO/Robots-Validate…	release-notes
http://www.openwall.com/lists/oss-security/2026/1…

Impacted products

1 product

Vendor	Product	Version	CPE status
		Affected: 0.4.3 , < 0.4.10 (custom)

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2026-10-22T00:16:41.831Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/10/21/30"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "modules": [
            "Robots::Validate"
          ],
          "packageName": "Robots-Validate",
          "packageURL": "pkg:cpan/Robots-Validate",
          "programFiles": [
            "lib/Robots/Validate.pm"
          ],
          "programRoutines": [
            {
              "name": "Robots::Validate::validate"
            },
            {
              "name": "Robots::Validate::bad_robot"
            }
          ],
          "repo": "https://github.com/robrwo/Robots-Validate",
          "versions": [
            {
              "lessThan": "0.4.10",
              "status": "affected",
              "version": "0.4.3",
              "versionType": "custom"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request.\n\nEach Robots::Validate object holds one pure-Perl Aho-Corasick search machine and feeds every User-Agent into it without resetting its state. A User-Agent that ends part-way through a robot name leaves the machine mid-match, so the next User-Agent checked by the same object can complete that name. That client\u0027s address is then checked against the robot\u0027s DNS rule, which it fails.\n\nA remote client can use this to make a site that blocks bad robots block other visitors where the prefix User-Agent string is a suffix of a robot being validated.\n\nNote that deployments with Algorithm::AhoCorasick::XS are also affected, since it was unused due to a different bug."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-488",
              "description": "CWE-488 Exposure of Data Element to Wrong Session",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-21T21:37:54.278Z",
        "orgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
        "shortName": "CPANSec"
      },
      "references": [
        {
          "tags": [
            "patch"
          ],
          "url": "https://github.com/robrwo/Robots-Validate/commit/776a1456e6605492b7582ed25d3d5006ef384402.patch"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.10/changes"
        },
        {
          "tags": [
            "release-notes"
          ],
          "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.11/changes"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to Robots-Validate v0.4.10 or later.\n\nDeployments with Algorithm::AhoCorasick::XS should upgrade to v0.4.11, which fixed a bug with using that version."
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "title": "Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request",
      "x_generator": {
        "engine": "cpansec-cna-tool 0.1"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
    "assignerShortName": "CPANSec",
    "cveId": "CVE-2026-112921",
    "datePublished": "2026-10-21T21:37:54.278Z",
    "dateReserved": "2026-10-19T21:17:46.149Z",
    "dateUpdated": "2026-10-22T00:16:41.831Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-112921",
      "date": "2026-10-26",
      "epss": "0.00229",
      "percentile": "0.13628"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "collectionURL": "https://cpan.org/modules",
                "defaultStatus": "unaffected",
                "modules": [
                  "Robots::Validate"
                ],
                "packageName": "Robots-Validate",
                "packageURL": "pkg:cpan/Robots-Validate",
                "programFiles": [
                  "lib/Robots/Validate.pm"
                ],
                "programRoutines": [
                  {
                    "name": "Robots::Validate::validate"
                  },
                  {
                    "name": "Robots::Validate::bad_robot"
                  }
                ],
                "repo": "https://github.com/robrwo/Robots-Validate",
                "versions": [
                  {
                    "lessThan": "0.4.10",
                    "status": "affected",
                    "version": "0.4.3",
                    "versionType": "custom"
                  }
                ]
              }
            ],
            "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request.\n\nEach Robots::Validate object holds one pure-Perl Aho-Corasick search machine and feeds every User-Agent into it without resetting its state. A User-Agent that ends part-way through a robot name leaves the machine mid-match, so the next User-Agent checked by the same object can complete that name. That client\u0027s address is then checked against the robot\u0027s DNS rule, which it fails.\n\nA remote client can use this to make a site that blocks bad robots block other visitors where the prefix User-Agent string is a suffix of a robot being validated.\n\nNote that deployments with Algorithm::AhoCorasick::XS are also affected, since it was unused due to a different bug."
          }
        ],
        "id": "CVE-2026-112921",
        "lastModified": "2026-10-22T17:40:46.877",
        "metrics": {},
        "published": "2026-10-21T22:16:48.527",
        "references": [
          {
            "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
            "url": "https://github.com/robrwo/Robots-Validate/commit/776a1456e6605492b7582ed25d3d5006ef384402.patch"
          },
          {
            "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
            "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.10/changes"
          },
          {
            "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
            "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.11/changes"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "url": "http://www.openwall.com/lists/oss-security/2026/10/21/30"
          }
        ],
        "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
        "vulnStatus": "Deferred",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-488"
              }
            ],
            "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
            "type": "Secondary"
          }
        ]
      }
    }
  }
}

FKIE_CVE-2026-112921

Vulnerability from fkie_nvd - Published: 2026-10-21 22:16 - Updated: 2026-10-22 17:40

Severity

Summary

References

	URL	Tags
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://github.com/robrwo/Robots-Validate/commit/776a1456e6605492b7582ed25d3d5006ef384402.patch
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://metacpan.org/release/RRWO/Robots-Validate-v0.4.10/changes
	9b29abf9-4ab0-4765-b253-1875cd9b441e	https://metacpan.org/release/RRWO/Robots-Validate-v0.4.11/changes
	af854a3a-2127-422b-91ae-364da2661108	http://www.openwall.com/lists/oss-security/2026/10/21/30

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "modules": [
            "Robots::Validate"
          ],
          "packageName": "Robots-Validate",
          "packageURL": "pkg:cpan/Robots-Validate",
          "programFiles": [
            "lib/Robots/Validate.pm"
          ],
          "programRoutines": [
            {
              "name": "Robots::Validate::validate"
            },
            {
              "name": "Robots::Validate::bad_robot"
            }
          ],
          "repo": "https://github.com/robrwo/Robots-Validate",
          "versions": [
            {
              "lessThan": "0.4.10",
              "status": "affected",
              "version": "0.4.3",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request.\n\nEach Robots::Validate object holds one pure-Perl Aho-Corasick search machine and feeds every User-Agent into it without resetting its state. A User-Agent that ends part-way through a robot name leaves the machine mid-match, so the next User-Agent checked by the same object can complete that name. That client\u0027s address is then checked against the robot\u0027s DNS rule, which it fails.\n\nA remote client can use this to make a site that blocks bad robots block other visitors where the prefix User-Agent string is a suffix of a robot being validated.\n\nNote that deployments with Algorithm::AhoCorasick::XS are also affected, since it was unused due to a different bug."
    }
  ],
  "id": "CVE-2026-112921",
  "lastModified": "2026-10-22T17:40:46.877",
  "metrics": {},
  "published": "2026-10-21T22:16:48.527",
  "references": [
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://github.com/robrwo/Robots-Validate/commit/776a1456e6605492b7582ed25d3d5006ef384402.patch"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.10/changes"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.11/changes"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/10/21/30"
    }
  ],
  "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-488"
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "type": "Secondary"
    }
  ]
}

GHSA-WH9J-9GH8-WM87

Vulnerability from github – Published: 2026-10-22 00:31 – Updated: 2026-10-22 03:33

Details

Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request.

Each Robots::Validate object holds one pure-Perl Aho-Corasick search machine and feeds every User-Agent into it without resetting its state. A User-Agent that ends part-way through a robot name leaves the machine mid-match, so the next User-Agent checked by the same object can complete that name. That client's address is then checked against the robot's DNS rule, which it fails.

A remote client can use this to make a site that blocks bad robots block other visitors where the prefix User-Agent string is a suffix of a robot being validated.

Note that deployments with Algorithm::AhoCorasick::XS are also affected, since it was unused due to a different bug.

Show details on source website

JSON

To clipboard

{
  "affected": [],
  "aliases": [
    "CVE-2026-112921"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-488"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-21T22:16:48Z",
    "severity": null
  },
  "details": "Robots::Validate versions from 0.4.3 before 0.4.10 for Perl report clients as imposter robots when User-Agent matcher state carries over from a previous request.\n\nEach Robots::Validate object holds one pure-Perl Aho-Corasick search machine and feeds every User-Agent into it without resetting its state. A User-Agent that ends part-way through a robot name leaves the machine mid-match, so the next User-Agent checked by the same object can complete that name. That client\u0027s address is then checked against the robot\u0027s DNS rule, which it fails.\n\nA remote client can use this to make a site that blocks bad robots block other visitors where the prefix User-Agent string is a suffix of a robot being validated.\n\nNote that deployments with Algorithm::AhoCorasick::XS are also affected, since it was unused due to a different bug.",
  "id": "GHSA-wh9j-9gh8-wm87",
  "modified": "2026-10-22T03:33:32Z",
  "published": "2026-10-22T00:31:58Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-112921"
    },
    {
      "type": "WEB",
      "url": "https://github.com/robrwo/Robots-Validate/commit/776a1456e6605492b7582ed25d3d5006ef384402.patch"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.10/changes"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/RRWO/Robots-Validate-v0.4.11/changes"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/10/21/30"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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.

Vulnerability timeline

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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-2026-112921 (GCVE-0-2026-112921)

FKIE_CVE-2026-112921

GHSA-WH9J-9GH8-WM87

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Related by attack behaviour