Vulnerability-Lookup

alsa-2026:1088

Vulnerability from osv_almalinux

Published

2026-01-26 00:00

Modified

2026-01-27 08:17

Summary

Important: python3.12-urllib3 security update

Details

Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems.

Security Fix(es):

urllib3: urllib3: Unbounded decompression chain leads to resource exhaustion (CVE-2025-66418)
urllib3: urllib3 Streaming API improperly handles highly compressed data (CVE-2025-66471)
urllib3: urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API) (CVE-2026-21441)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "AlmaLinux:9",
        "name": "python3.12-urllib3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.26.19-1.el9_7.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "details": "Python is an interpreted, interactive, object-oriented programming language, which includes modules, classes, exceptions, very high level dynamic data types and dynamic typing. Python supports interfaces to many system calls and libraries, as well as to various windowing systems.  \n\nSecurity Fix(es):  \n\n  * urllib3: urllib3: Unbounded decompression chain leads to resource exhaustion (CVE-2025-66418)\n  * urllib3: urllib3 Streaming API improperly handles highly compressed data (CVE-2025-66471)\n  * urllib3: urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API) (CVE-2026-21441)\n\n\nFor more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.\n",
  "id": "ALSA-2026:1088",
  "modified": "2026-01-27T08:17:27Z",
  "published": "2026-01-26T00:00:00Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://access.redhat.com/errata/RHSA-2026:1088"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2025-66418"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2025-66471"
    },
    {
      "type": "REPORT",
      "url": "https://access.redhat.com/security/cve/CVE-2026-21441"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2419455"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2419467"
    },
    {
      "type": "REPORT",
      "url": "https://bugzilla.redhat.com/2427726"
    },
    {
      "type": "ADVISORY",
      "url": "https://errata.almalinux.org/9/ALSA-2026-1088.html"
    }
  ],
  "related": [
    "CVE-2025-66418",
    "CVE-2025-66471",
    "CVE-2026-21441"
  ],
  "summary": "Important: python3.12-urllib3 security update"
}

CVE-2026-21441 (GCVE-0-2026-21441)

Vulnerability from cvelistv5 – Published: 2026-01-07 22:09 – Updated: 2026-01-23 09:07

Title

urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)

Summary

urllib3 is an HTTP client library for Python. urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. urllib3 can perform decoding or decompression based on the HTTP `Content-Encoding` header (e.g., `gzip`, `deflate`, `br`, or `zstd`). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption. Starting in version 1.22 and prior to version 2.6.3, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client. Applications and libraries are affected when they stream content from untrusted sources by setting `preload_content=False` when they do not disable redirects. Users should upgrade to at least urllib3 v2.6.3, in which the library does not decode content of redirect responses when `preload_content=False`. If upgrading is not immediately possible, disable redirects by setting `redirect=False` for requests to untrusted source.

Severity ?

8.9 (High)


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

CWE

CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)

Assigner

GitHub_M

References

URL

Tags

	https://github.com/urllib3/urllib3/security/advis…	x_refsource_CONFIRM
	https://github.com/urllib3/urllib3/commit/8864ac4…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	urllib3	urllib3	Affected: >= 1.22, < 2.6.3

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
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        "title": "CISA ADP Vulnrichment"
      },
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        "references": [
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            "url": "https://lists.debian.org/debian-lts-announce/2026/01/msg00017.html"
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          "vendor": "urllib3",
          "versions": [
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              "version": "\u003e= 1.22, \u003c 2.6.3"
            }
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          "value": "urllib3 is an HTTP client library for Python. urllib3\u0027s streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. urllib3 can perform decoding or decompression based on the HTTP `Content-Encoding` header (e.g., `gzip`, `deflate`, `br`, or `zstd`). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption. Starting in version 1.22 and prior to version 2.6.3, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client. Applications and libraries are affected when they stream content from untrusted sources by setting `preload_content=False` when they do not disable redirects. Users should upgrade to at least urllib3 v2.6.3, in which the library does not decode content of redirect responses when `preload_content=False`. If upgrading is not immediately possible, disable redirects by setting `redirect=False` for requests to untrusted source."
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            "subAvailabilityImpact": "HIGH",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
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        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
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      },
      "references": [
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          "name": "https://github.com/urllib3/urllib3/security/advisories/GHSA-38jv-5279-wg99",
          "tags": [
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          ],
          "url": "https://github.com/urllib3/urllib3/security/advisories/GHSA-38jv-5279-wg99"
        },
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          "tags": [
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          "url": "https://github.com/urllib3/urllib3/commit/8864ac407bba8607950025e0979c4c69bc7abc7b"
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      "source": {
        "advisory": "GHSA-38jv-5279-wg99",
        "discovery": "UNKNOWN"
      },
      "title": "urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)"
    }
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  "cveMetadata": {
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    "datePublished": "2026-01-07T22:09:01.936Z",
    "dateReserved": "2025-12-29T03:00:29.276Z",
    "dateUpdated": "2026-01-23T09:07:22.785Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

CVE-2025-66471 (GCVE-0-2025-66471)

Vulnerability from cvelistv5 – Published: 2025-12-05 16:06 – Updated: 2025-12-05 19:33

Title

urllib3 Streaming API improperly handles highly compressed data

Summary

urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.0 and prior to 2.6.0, the Streaming API improperly handles highly compressed data. urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation. The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data.

Severity ?

8.9 (High)


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

CWE

CWE-409 - Improper Handling of Highly Compressed Data (Data Amplification)

Assigner

GitHub_M

References

URL

Tags

	https://github.com/urllib3/urllib3/security/advis…	x_refsource_CONFIRM
	https://github.com/urllib3/urllib3/commit/c19571d…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	urllib3	urllib3	Affected: >= 1.0, < 2.6.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
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                "id": "CVE-2025-66471",
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            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H",
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          ],
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  "dataVersion": "5.2"
}

CVE-2025-66418 (GCVE-0-2025-66418)

Vulnerability from cvelistv5 – Published: 2025-12-05 16:02 – Updated: 2025-12-05 18:15

Title

urllib3 allows an unbounded number of links in the decompression chain

Summary

urllib3 is a user-friendly HTTP client library for Python. Starting in version 1.24 and prior to 2.6.0, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data. This vulnerability is fixed in 2.6.0.

Severity ?

8.9 (High)


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

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M

References

URL

Tags

	https://github.com/urllib3/urllib3/security/advis…	x_refsource_CONFIRM
	https://github.com/urllib3/urllib3/commit/24d7b67…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	urllib3	urllib3	Affected: >= 1.24, < 2.6.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-66418",
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                  },
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                    "Technical Impact": "partial"
                  }
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                "role": "CISA Coordinator",
                "timestamp": "2025-12-05T16:15:39.701596Z",
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        },
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      }
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          "versions": [
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        }
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        {
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            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
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            "subConfidentialityImpact": "NONE",
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        },
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          "url": "https://github.com/urllib3/urllib3/commit/24d7b67eac89f94e11003424bcf0d8f7b72222a8"
        }
      ],
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        "advisory": "GHSA-gm62-xv2j-4w53",
        "discovery": "UNKNOWN"
      },
      "title": "urllib3 allows an unbounded number of links in the decompression chain"
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    "assignerShortName": "GitHub_M",
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    "datePublished": "2025-12-05T16:02:15.271Z",
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    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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}

Tags

Taxonomy of the tags.

All sightings related to this event Export sightings related to this event

Sightings

Author	Source	Type	Date

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

alsa-2026:1088

Vulnerability from osv_almalinux

CVE-2026-21441 (GCVE-0-2026-21441)

CVE-2025-66471 (GCVE-0-2025-66471)

CVE-2025-66418 (GCVE-0-2025-66418)

Tags

Sightings

Nomenclature