Vulnerability-Lookup

UBUNTU-CVE-2026-97688 (CVE-2026-97688)

Vulnerability from osv_ubuntu – Published: 2026-09-29 16:17 – Updated: 2026-09-29 16:17 – Source website

Details

urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0.

Severity

6.9 (Medium)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-97688	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-97688	REPORT
	https://github.com/urllib3/urllib3/security/advis…	REPORT
	https://github.com/urllib3/urllib3/commit/ea2ad7b…	REPORT
	https://github.com/urllib3/urllib3/releases/tag/2.8.0	REPORT

JSON

To clipboard

{
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      "ecosystem_specific": {
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          {
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            "binary_version": "1.5.4-1ubuntu4+esm5"
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            "binary_version": "1.5.4-1ubuntu4+esm5"
          }
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      "package": {
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        "purl": "pkg:deb/ubuntu/python-pip@1.5.4-1ubuntu4+esm5?arch=source\u0026distro=esm-infra-legacy/trusty"
      },
      "ranges": [
        {
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            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.4.1-2",
        "1.5.4-1",
        "1.5.4-1ubuntu1",
        "1.5.4-1ubuntu3",
        "1.5.4-1ubuntu4",
        "1.5.4-1ubuntu4+esm1",
        "1.5.4-1ubuntu4+esm2",
        "1.5.4-1ubuntu4+esm3",
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        "25.1.1+dfsg-1ubuntu2+esm2",
        "25.1.1+dfsg-1ubuntu2+esm3"
      ]
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  ],
  "aliases": [],
  "details": "urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0.",
  "id": "UBUNTU-CVE-2026-97688",
  "modified": "2026-09-29T16:17:00Z",
  "published": "2026-09-29T16:17:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-97688"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-97688"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/urllib3/urllib3/releases/tag/2.8.0"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-97688"
  ]
}

CVE-2026-97688 (GCVE-0-2026-97688)

Vulnerability from cvelistv5 – Published: 2026-09-29 15:32 – Updated: 2026-09-29 15:42

Title

urllib3: Chunked Deflate streaming can enter an infinite loop

Summary

Severity

6.9 (Medium)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-29 15:42 UTC

CWE

CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/urllib3/urllib3/security/advis…	x_refsource_CONFIRM
https://github.com/urllib3/urllib3/commit/ea2ad7b…	x_refsource_MISC
https://github.com/urllib3/urllib3/releases/tag/2.8.0	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
urllib3	urllib3	Affected: >= 2.6.2, < 2.8.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-97688",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-29T15:42:28.931695Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-29T15:42:34.502Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "urllib3",
          "vendor": "urllib3",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.6.2, \u003c 2.8.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "urllib3 is an HTTP client library for Python. From 2.6.2 until 2.8.0, HTTPResponse.stream and HTTPResponse.read_chunked can enter an infinite loop because the Deflate decoder retains trailing bytes as unconsumed input after reaching end-of-stream and repeatedly decodes them without progress. The issue occurs when an untrusted server sends a chunked Deflate response whose decoded body exceeds a positive finite chunk size and whose encoded body has trailing bytes, specifically a response with Transfer-Encoding: chunked and Content-Encoding: deflate, content decoding enabled, and the positive finite amt=N streaming chunk size. The attack mechanism is that a malicious server returns a compressed chunked response with trailing bytes after the Deflate stream. The impact is excessive CPU usage and a request that does not complete, and network read timeouts do not interrupt the loop because no further socket read occurs. This issue is fixed in version 2.8.0."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 6.9,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-835",
              "description": "CWE-835: Loop with Unreachable Exit Condition (\u0027Infinite Loop\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-29T15:32:17.622Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g"
        },
        {
          "name": "https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f"
        },
        {
          "name": "https://github.com/urllib3/urllib3/releases/tag/2.8.0",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/urllib3/urllib3/releases/tag/2.8.0"
        }
      ],
      "source": {
        "advisory": "GHSA-gh4c-6fx4-qh6g",
        "discovery": "UNKNOWN"
      },
      "title": "urllib3: Chunked Deflate streaming can enter an infinite loop"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-97688",
    "datePublished": "2026-09-29T15:32:17.622Z",
    "dateReserved": "2026-09-24T21:43:37.208Z",
    "dateUpdated": "2026-09-29T15:42:34.502Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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

UBUNTU-CVE-2026-97688 (CVE-2026-97688)

CVE-2026-97688 (GCVE-0-2026-97688)

Tags

Sightings

Nomenclature

Related by attack behaviour