Vulnerability-Lookup

PYSEC-2026-251

Vulnerability from pysec - Published: 2026-06-22 22:16 - Updated: 2026-06-27 10:30

Details

WebOb provides objects for HTTP requests and responses. Prior to 1.8.10, the normalization of the HTTP Location header during a redirect is vulnerable to an open redirect: WebOb joins the redirect target to the request URI using Python's urljoin, and since Python 3.10 the underlying urlsplit strips ASCII tab, carriage return, and newline characters before parsing, so a redirect target containing such characters can be reinterpreted as a protocol-relative URL whose authority is an attacker-controlled host. This bypasses the CVE-2024-42353 fix that escaped a leading double slash, allowing an attacker who influences the redirect location to send users to an arbitrary external site instead of the intended one. This vulnerability is fixed in 1.8.10.

Severity

6.1 (Medium)


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

Impacted products

Name	purl
webob	pkg:pypi/webob

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "PyPI",
        "name": "webob",
        "purl": "pkg:pypi/webob"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.8",
        "0.8.1",
        "0.8.2",
        "0.8.3",
        "0.8.4",
        "0.8.5",
        "0.9",
        "0.9.1",
        "0.9.2",
        "0.9.3",
        "0.9.4",
        "0.9.5",
        "0.9.6",
        "0.9.6.1",
        "0.9.7",
        "0.9.7.1",
        "0.9.8",
        "1.0",
        "1.0.1",
        "1.0.2",
        "1.0.3",
        "1.0.4",
        "1.0.5",
        "1.0.6",
        "1.0.7",
        "1.0.8",
        "1.1",
        "1.1.1",
        "1.1b2",
        "1.1beta1",
        "1.1rc1",
        "1.2",
        "1.2.1",
        "1.2.2",
        "1.2.3",
        "1.2b1",
        "1.2b2",
        "1.2b3",
        "1.2rc1",
        "1.3",
        "1.3.1",
        "1.4",
        "1.4.1",
        "1.4.2",
        "1.5.0",
        "1.5.0a0",
        "1.5.0a1",
        "1.5.0b0",
        "1.5.1",
        "1.6.0",
        "1.6.0a0",
        "1.6.1",
        "1.6.2",
        "1.6.3",
        "1.6.4",
        "1.7.0",
        "1.7.0rc1",
        "1.7.0rc2",
        "1.7.1",
        "1.7.2",
        "1.7.3",
        "1.7.4",
        "1.8.0",
        "1.8.0rc1",
        "1.8.1",
        "1.8.2",
        "1.8.3",
        "1.8.4",
        "1.8.5",
        "1.8.6",
        "1.8.7",
        "1.8.8",
        "1.8.9"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44889",
    "GHSA-fh3h-vg37-cc95"
  ],
  "details": "WebOb provides objects for HTTP requests and responses. Prior to 1.8.10, the normalization of the HTTP Location header during a redirect is vulnerable to an open redirect: WebOb joins the redirect target to the request URI using Python\u0027s urljoin, and since Python 3.10 the underlying urlsplit strips ASCII tab, carriage return, and newline characters before parsing, so a redirect target containing such characters can be reinterpreted as a protocol-relative URL whose authority is an attacker-controlled host. This bypasses the CVE-2024-42353 fix that escaped a leading double slash, allowing an attacker who influences the redirect location to send users to an arbitrary external site instead of the intended one. This vulnerability is fixed in 1.8.10.",
  "id": "PYSEC-2026-251",
  "modified": "2026-06-27T10:30:05.092304Z",
  "published": "2026-06-22T22:16:46.350Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/Pylons/webob/security/advisories/GHSA-fh3h-vg37-cc95"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-44889 (GCVE-0-2026-44889)

Vulnerability from cvelistv5 – Published: 2026-06-22 21:30 – Updated: 2026-06-23 15:05

Title

WebOb: Location header normalization during redirect leads to open redirect

Summary

Severity

6.1 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-601 - URL Redirection to Untrusted Site ('Open Redirect')

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/Pylons/webob/security/advisori…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
Pylons	webob	Affected: < 1.8.10

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-44889",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-23T14:58:48.576241Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-23T15:05:27.698Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "webob",
          "vendor": "Pylons",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.8.10"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "WebOb provides objects for HTTP requests and responses. Prior to 1.8.10, the normalization of the HTTP Location header during a redirect is vulnerable to an open redirect: WebOb joins the redirect target to the request URI using Python\u0027s urljoin, and since Python 3.10 the underlying urlsplit strips ASCII tab, carriage return, and newline characters before parsing, so a redirect target containing such characters can be reinterpreted as a protocol-relative URL whose authority is an attacker-controlled host. This bypasses the CVE-2024-42353 fix that escaped a leading double slash, allowing an attacker who influences the redirect location to send users to an arbitrary external site instead of the intended one. This vulnerability is fixed in 1.8.10."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 6.1,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-601",
              "description": "CWE-601: URL Redirection to Untrusted Site (\u0027Open Redirect\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-22T21:30:11.789Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/Pylons/webob/security/advisories/GHSA-fh3h-vg37-cc95",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/Pylons/webob/security/advisories/GHSA-fh3h-vg37-cc95"
        }
      ],
      "source": {
        "advisory": "GHSA-fh3h-vg37-cc95",
        "discovery": "UNKNOWN"
      },
      "title": "WebOb: Location header normalization during redirect leads to open redirect"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-44889",
    "datePublished": "2026-06-22T21:30:11.789Z",
    "dateReserved": "2026-05-07T21:50:33.545Z",
    "dateUpdated": "2026-06-23T15:05:27.698Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-FH3H-VG37-CC95

Vulnerability from github – Published: 2026-06-04 14:33 – Updated: 2026-06-04 14:33

Summary

WebOb: Location header normalization during redirect leads to open redirect - again

Details

Impact

When WebOb normalizes the HTTP Location header to include the request hostname, it does so by parsing the URL that the user is to be redirected to with Python's urllib.parse, and joining it to the base URL. urlsplit (called internally by urljoin) however treats a // at the start of a string as a URI without a scheme, and then treats the next part as the hostname. urljoin will then use that hostname from the second part as the hostname replacing the original one from the request.

In a previous advisory https://github.com/Pylons/webob/security/advisories/GHSA-mg3v-6m49-jhp3 an attempt to fix this was made by forcing the replacement of // with /%2f, however this did not take into account that since Python 3.10 urlsplit internally strips ASCII tab, carriage return, and newline characters from the string, so /\t/attacker.com gets turned into //attacker.com and the attacker is able to bypass the changes introduced in that previous advisory, thereby bringing back the problem that was attempted to be fixed.

>>> parse.urlparse("//attacker.com/some/path")
ParseResult(scheme='', netloc='attacker.com', path='/some/path', params='', query='', fragment='')

WebOb uses urljoin to take the request URI and join the redirect location to it, so assuming the request URI is https://example.org/ and the URL to redirect to is /\t/attacker.com/some/path/:

>>> parse.urljoin("https://example.org/", "/\t/attacker.com/some/path/")
'https://attacker.com/some/path/'

Which redirects from example.org where we want the user to stay to attacker.com.

Patches

This issue has been fixed in WebOb 1.8.10.

Workarounds

Any use of the Response class that includes a location can be rewritten to make sure to always pass a full URI that includes the hostname to redirect the user to, or to validate that the redirect target starts with a scheme (e.g. http:// or https://) before assigning to Response.location.

References

https://github.com/Pylons/webob/security/advisories/GHSA-mg3v-6m49-jhp3
CVE-2024-42353

Thanks

Caleb Brown of Google

Severity

6.1 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.8.9"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "webob"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.8.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44889"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-601"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-04T14:33:35Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nWhen WebOb normalizes the HTTP Location header to include the request hostname, it does so by parsing the URL that the user is to be redirected to with Python\u0027s `urllib.parse`, and joining it to the base URL. `urlsplit` (called internally by `urljoin`) however treats a `//` at the start of a string as a URI without a scheme, and then treats the next part as the hostname. `urljoin` will then use that hostname from the second part as the hostname replacing the original one from the request.\n\nIn a previous advisory https://github.com/Pylons/webob/security/advisories/GHSA-mg3v-6m49-jhp3 an attempt to fix this was made by forcing the replacement of `//` with `/%2f`, however this did not take into account that since Python 3.10 `urlsplit` internally strips ASCII tab, carriage return, and newline characters from the string, so `/\\t/attacker.com` gets turned into `//attacker.com` and the attacker is able to bypass the changes introduced in that previous advisory, thereby bringing back the problem that was attempted to be fixed.\n\n```\n\u003e\u003e\u003e parse.urlparse(\"//attacker.com/some/path\")\nParseResult(scheme=\u0027\u0027, netloc=\u0027attacker.com\u0027, path=\u0027/some/path\u0027, params=\u0027\u0027, query=\u0027\u0027, fragment=\u0027\u0027)\n```\n\nWebOb uses `urljoin` to take the request URI and join the redirect location to it, so assuming the request URI is `https://example.org/` and the URL to redirect to is `/\\t/attacker.com/some/path/`:\n\n```\n\u003e\u003e\u003e parse.urljoin(\"https://example.org/\", \"/\\t/attacker.com/some/path/\")\n\u0027https://attacker.com/some/path/\u0027\n```\n\nWhich redirects from `example.org` where we want the user to stay to `attacker.com`.\n\n### Patches\n\nThis issue has been fixed in WebOb 1.8.10.\n\n### Workarounds\n\nAny use of the `Response` class that includes a `location` can be rewritten to make sure to always pass a full URI that includes the hostname to redirect the user to, or to validate that the redirect target starts with a scheme (e.g. `http://` or `https://`) before assigning to `Response.location`.\n\n### References\n\n- https://github.com/Pylons/webob/security/advisories/GHSA-mg3v-6m49-jhp3\n- CVE-2024-42353\n\n### Thanks\n\n- Caleb Brown of Google",
  "id": "GHSA-fh3h-vg37-cc95",
  "modified": "2026-06-04T14:33:35Z",
  "published": "2026-06-04T14:33:35Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Pylons/webob/security/advisories/GHSA-fh3h-vg37-cc95"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Pylons/webob/security/advisories/GHSA-mg3v-6m49-jhp3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Pylons/webob/commit/1f681a4f17fc10777ef861e8b43ecb26053bc539"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Pylons/webob/commit/2b9fbedafb31180c910cf8526e9ea72b4603d0bc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Pylons/webob"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Pylons/webob/releases/tag/1.8.10"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "WebOb: Location header normalization during redirect leads to open redirect - again"
}

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.

Action not permitted

PYSEC-2026-251

CVE-2026-44889 (GCVE-0-2026-44889)

GHSA-FH3H-VG37-CC95

Impact

Patches

Workarounds

References

Thanks

Tags

Sightings

Nomenclature