Common Weakness Enumeration

CWE-835

Allowed

Loop with Unreachable Exit Condition ('Infinite Loop')

Abstraction: Base · Status: Incomplete

API response cwe.mitre.org

The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

1314 vulnerabilities reference this CWE, most recent first.

GHSA-GC74-G85R-W7X5

Vulnerability from github – Published: 2026-07-27 18:31 – Updated: 2026-07-31 21:31
VLAI
Details

facil.io 0.6.0 through 0.7.6 contains a denial-of-service vulnerability in the multipart body parser that allows an unauthenticated remote attacker to permanently freeze worker processes at 100% CPU by sending a multipart/form-data request with a partial closing boundary. The missing progress guard in the parser loop causes http_mime_parse to return 0 bytes consumed without setting done or error flags, causing the calling loop to re-invoke the parser on the same buffer indefinitely, exhausting all workers and permanently disabling the server until manually restarted.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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{
  "affected": [],
  "aliases": [
    "CVE-2026-66730"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-27T17:16:42Z",
    "severity": "HIGH"
  },
  "details": "facil.io 0.6.0 through 0.7.6 contains a denial-of-service vulnerability in the multipart body parser that allows an unauthenticated remote attacker to permanently freeze worker processes at 100% CPU by sending a multipart/form-data request with a partial closing boundary. The missing progress guard in the parser loop causes http_mime_parse to return 0 bytes consumed without setting done or error flags, causing the calling loop to re-invoke the parser on the same buffer indefinitely, exhausting all workers and permanently disabling the server until manually restarted.",
  "id": "GHSA-gc74-g85r-w7x5",
  "modified": "2026-07-31T21:31:50Z",
  "published": "2026-07-27T18:31:49Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-66730"
    },
    {
      "type": "WEB",
      "url": "https://github.com/theopaid/Infinite-Loop-DoS-in-facil.io-MIME-Parser"
    },
    {
      "type": "WEB",
      "url": "https://tpaidakis.com/writeups/facilio-parser-dos"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/facil-io-infinite-loop-dos-via-multipart-mime-body-parser"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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"
    }
  ]
}

GHSA-GF7X-HG8H-X3GF

Vulnerability from github – Published: 2026-08-14 18:31 – Updated: 2026-08-14 18:31
VLAI
Details

A flow has been identified into dnssec.c library, causing an infinite loop to dnsmasq service. An attacker who controls any DNSSEC-signed zone can hang the dnsmasq process with a single crafted response, killing all DNS resolution for its clients.

Severity
4.4 (Medium)
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [],
  "aliases": [
    "CVE-2026-13002"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-14T16:16:49Z",
    "severity": "MODERATE"
  },
  "details": "A flow has been identified into dnssec.c library, causing an infinite loop to dnsmasq service. An attacker who controls any DNSSEC-signed zone can hang the dnsmasq process with a single crafted response, killing all DNS resolution for its clients.",
  "id": "GHSA-gf7x-hg8h-x3gf",
  "modified": "2026-08-14T18:31:37Z",
  "published": "2026-08-14T18:31:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-13002"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/security/cve/CVE-2026-13002"
    },
    {
      "type": "WEB",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2486360"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-GFH2-7JG5-653P

Vulnerability from github – Published: 2022-02-15 01:57 – Updated: 2021-05-20 16:29
VLAI
Summary
Denial of Service in docker2aci
Details

docker2aci <= 0.12.3 has an infinite loop when handling local images with cyclic dependency chain.

Severity
4.0 (Medium)
CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/appc/docker2aci"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.13.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2016-8579"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2021-05-20T16:29:42Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "docker2aci \u003c= 0.12.3 has an infinite loop when handling local images with cyclic dependency chain.",
  "id": "GHSA-gfh2-7jg5-653p",
  "modified": "2021-05-20T16:29:42Z",
  "published": "2022-02-15T01:57:18Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2016-8579"
    },
    {
      "type": "WEB",
      "url": "https://github.com/appc/docker2aci/issues/203"
    },
    {
      "type": "WEB",
      "url": "https://github.com/appc/docker2aci/pull/204/commits/54331ec7020e102935c31096f336d31f6400064f"
    },
    {
      "type": "WEB",
      "url": "https://github.com/appc/docker2aci/releases/tag/v0.13.0"
    },
    {
      "type": "WEB",
      "url": "https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-8579"
    },
    {
      "type": "WEB",
      "url": "https://www.securityfocus.com/bid/93560"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Denial of Service in docker2aci"
}

GHSA-GFR2-Q5Q8-V55V

Vulnerability from github – Published: 2026-06-25 09:31 – Updated: 2026-06-28 09:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

timers/migration: Fix livelock in tmigr_handle_remote_up()

tmigr_handle_remote_cpu() skips timer_expire_remote() when cpu == smp_processor_id(), assuming the local softirq path already handled this CPU's timers.

This assumption is wrong because jiffies can advance after the handling of the CPU's global timers in run_timer_base(BASE_GLOBAL) and before tmigr_handle_remote() evaluates the expiry times.

As a consequence a timer which expires after the CPU local timer wheel advanced and becomes expired in the remote handling is ignored and the callback is never invoked and removed from the timer wheel.

What's worse is that fetch_next_timer_interrupt_remote() keeps reporting it as expired, and the event is re-queued with expires == now on each iteration. The goto-again loop spins indefinitely.

Fix this by calling timer_expire_remote() unconditionally. That's minimal overhead for the common case as __run_timer_base() returns immediately if there is nothing to expire in the local wheel.

[ tglx: Amend change log and add a comment ]

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2026-53180"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-667",
      "CWE-835"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-06-25T09:16:35Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntimers/migration: Fix livelock in tmigr_handle_remote_up()\n\ntmigr_handle_remote_cpu() skips timer_expire_remote() when cpu ==\nsmp_processor_id(), assuming the local softirq path already handled this\nCPU\u0027s timers.\n\nThis assumption is wrong because jiffies can advance after the handling of\nthe CPU\u0027s global timers in run_timer_base(BASE_GLOBAL) and before\ntmigr_handle_remote() evaluates the expiry times.\n\nAs a consequence a timer which expires after the CPU local timer wheel\nadvanced and becomes expired in the remote handling is ignored and the\ncallback is never invoked and removed from the timer wheel.\n\nWhat\u0027s worse is that fetch_next_timer_interrupt_remote() keeps reporting it\nas expired, and the event is re-queued with expires == now on each\niteration.  The goto-again loop spins indefinitely.\n\nFix this by calling timer_expire_remote() unconditionally. That\u0027s minimal\noverhead for the common case as __run_timer_base() returns immediately if\nthere is nothing to expire in the local wheel.\n\n[ tglx: Amend change log and add a comment ]",
  "id": "GHSA-gfr2-q5q8-v55v",
  "modified": "2026-06-28T09:31:43Z",
  "published": "2026-06-25T09:31:20Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53180"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/07b3b83587fb3012619f4439389b64a955fc7836"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1d6c2062b77be09ec15d6bf637b2e2221c4482fc"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d338e61ea94052a786aac9f58e9f0d8520afa0fd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d486b4934a8e504376b85cdb3766f306d57aff5b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-GFVH-R99J-X28P

Vulnerability from github – Published: 2022-05-24 17:41 – Updated: 2022-05-24 17:41
VLAI
Details

Hirschmann OS2, RSP, and RSPE devices before HiOS 08.3.00 allow a denial of service. An unauthenticated, adjacent attacker can cause an infinite loop on one of the HSR ring ports of the device. This effectively breaks the redundancy of the HSR ring. If the attacker can perform the same attack on a second device, the ring is broken into two parts (thus disrupting communication between devices in the different parts).

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{
  "affected": [],
  "aliases": [
    "CVE-2020-9307"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2021-02-11T21:15:00Z",
    "severity": "MODERATE"
  },
  "details": "Hirschmann OS2, RSP, and RSPE devices before HiOS 08.3.00 allow a denial of service. An unauthenticated, adjacent attacker can cause an infinite loop on one of the HSR ring ports of the device. This effectively breaks the redundancy of the HSR ring. If the attacker can perform the same attack on a second device, the ring is broken into two parts (thus disrupting communication between devices in the different parts).",
  "id": "GHSA-gfvh-r99j-x28p",
  "modified": "2022-05-24T17:41:54Z",
  "published": "2022-05-24T17:41:54Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-9307"
    },
    {
      "type": "WEB",
      "url": "https://www.belden.com/dfsmedia/f1e38517e0cd4caa8b1acb6619890f5e/12276-source/options/view"
    },
    {
      "type": "WEB",
      "url": "https://www.belden.com/security"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

GHSA-GFVQ-MXW3-MFQ3

Vulnerability from github – Published: 2023-10-03 06:30 – Updated: 2023-10-04 19:34
VLAI
Summary
asyncua vulnerable to denial of service via infinite loop
Details

Versions of the package asyncua before 0.9.96 are vulnerable to Denial of Service (DoS) such that an attacker can send a malformed packet and as a result, the server will enter into an infinite loop and consume excessive memory.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "asyncua"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.9.96"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2023-26151"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2023-10-04T14:19:07Z",
    "nvd_published_at": "2023-10-03T05:15:50Z",
    "severity": "HIGH"
  },
  "details": "Versions of the package asyncua before 0.9.96 are vulnerable to Denial of Service (DoS) such that an attacker can send a malformed packet and as a result, the server will enter into an infinite loop and consume excessive memory.",
  "id": "GHSA-gfvq-mxw3-mfq3",
  "modified": "2023-10-04T19:34:19Z",
  "published": "2023-10-03T06:30:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-26151"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FreeOpcUa/opcua-asyncio/issues/1013"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FreeOpcUa/opcua-asyncio/pull/1039"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FreeOpcUa/opcua-asyncio/commit/f6603daa34a93a658f0e176cb0b9ee5a6643b262"
    },
    {
      "type": "WEB",
      "url": "https://gist.github.com/artfire52/1540b234350795e0ecb4d672608dbec8"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/FreeOpcUa/opcua-asyncio"
    },
    {
      "type": "WEB",
      "url": "https://github.com/FreeOpcUa/opcua-asyncio/releases/tag/v0.9.96"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/asyncua/PYSEC-2023-190.yaml"
    },
    {
      "type": "WEB",
      "url": "https://security.snyk.io/vuln/SNYK-PYTHON-ASYNCUA-5673709"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "asyncua vulnerable to denial of service via infinite loop"
}

GHSA-GGGQ-J347-R3W6

Vulnerability from github – Published: 2025-03-27 15:31 – Updated: 2025-11-03 21:33
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

tee: optee: Fix supplicant wait loop

OP-TEE supplicant is a user-space daemon and it's possible for it be hung or crashed or killed in the middle of processing an OP-TEE RPC call. It becomes more complicated when there is incorrect shutdown ordering of the supplicant process vs the OP-TEE client application which can eventually lead to system hang-up waiting for the closure of the client application.

Allow the client process waiting in kernel for supplicant response to be killed rather than indefinitely waiting in an unkillable state. Also, a normal uninterruptible wait should not have resulted in the hung-task watchdog getting triggered, but the endless loop would.

This fixes issues observed during system reboot/shutdown when supplicant got hung for some reason or gets crashed/killed which lead to client getting hung in an unkillable state. It in turn lead to system being in hung up state requiring hard power off/on to recover.

Severity
5.5 (Medium)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2025-21871"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-03-27T14:15:48Z",
    "severity": "MODERATE"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntee: optee: Fix supplicant wait loop\n\nOP-TEE supplicant is a user-space daemon and it\u0027s possible for it\nbe hung or crashed or killed in the middle of processing an OP-TEE\nRPC call. It becomes more complicated when there is incorrect shutdown\nordering of the supplicant process vs the OP-TEE client application which\ncan eventually lead to system hang-up waiting for the closure of the\nclient application.\n\nAllow the client process waiting in kernel for supplicant response to\nbe killed rather than indefinitely waiting in an unkillable state. Also,\na normal uninterruptible wait should not have resulted in the hung-task\nwatchdog getting triggered, but the endless loop would.\n\nThis fixes issues observed during system reboot/shutdown when supplicant\ngot hung for some reason or gets crashed/killed which lead to client\ngetting hung in an unkillable state. It in turn lead to system being in\nhung up state requiring hard power off/on to recover.",
  "id": "GHSA-gggq-j347-r3w6",
  "modified": "2025-11-03T21:33:13Z",
  "published": "2025-03-27T15:31:09Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21871"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0180cf0373f84fff61b16f8c062553a13dd7cfca"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/21234efe2a8474a6d2d01ea9573319de7858ce44"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/3eb4911364c764572e9db4ab900a57689a54e8ce"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/70b0d6b0a199c5a3ee6c72f5e61681ed6f759612"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c0a9a948159153be145f9471435695373904ee6d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d61cc1a435e6894bfb0dd3370c6f765d2d12825d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ec18520f5edc20a00c34a8c9fdd6507c355e880f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fd9d2d6124c293e40797a080adf8a9c237efd8b8"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-GH28-WW79-7H4V

Vulnerability from github – Published: 2026-05-12 00:31 – Updated: 2026-07-18 03:31
VLAI
Details

barebox version prior to 2026.04.0 contains a denial-of-service vulnerability in ext4 directory parsing in fs/ext4/ext4_common.c where the ext4fs_iterate_dir() function fails to validate that directory entry length values are non-zero. Attackers can supply a malicious ext4 filesystem image with a crafted directory entry containing a direntlen value of 0 to cause an infinite loop during directory listing or path resolution, resulting in the boot process hanging indefinitely.

Severity
6.2 (Medium)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.9 (Medium)
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2026-34962"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-11T23:19:47Z",
    "severity": "MODERATE"
  },
  "details": "barebox version prior to 2026.04.0 contains a denial-of-service vulnerability in ext4 directory parsing in fs/ext4/ext4_common.c where the ext4fs_iterate_dir() function fails to validate that directory entry length values are non-zero. Attackers can supply a malicious ext4 filesystem image with a crafted directory entry containing a direntlen value of 0 to cause an infinite loop during directory listing or path resolution, resulting in the boot process hanging indefinitely.",
  "id": "GHSA-gh28-ww79-7h4v",
  "modified": "2026-07-18T03:31:04Z",
  "published": "2026-05-12T00:31:15Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34962"
    },
    {
      "type": "WEB",
      "url": "https://github.com/barebox/barebox"
    },
    {
      "type": "WEB",
      "url": "https://github.com/barebox/barebox/releases/tag/v2026.04.0"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/barebox-ext4-directory-parsing-infinite-loop-denial-of-service"
    },
    {
      "type": "WEB",
      "url": "https://y637f9qq2x.com/posts/barebox-sandbox-vulns"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/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"
    }
  ]
}

GHSA-GH4C-6FX4-QH6G

Vulnerability from github – Published: 2026-09-30 15:00 – Updated: 2026-09-30 15:00
VLAI
Summary
urllib3: Chunked Deflate streaming can enter an infinite loop
Details

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading content in chunks instead of loading the entire response body into memory at once.

urllib3 can decompress response bodies according to the HTTP Content-Encoding header. When streaming a compressed, chunked response, urllib3 first consumes data already buffered by the decoder before reading the next HTTP chunk.

However, urllib3 versions from 2.6.2 through 2.7.0 could enter an infinite loop when a chunked response contained bytes after the end of the Deflate stream. If the decompressed body exceeded the requested streaming chunk size, Python's zlib implementation could retain the trailing bytes as unconsumed input after reaching the end of the compressed stream. urllib3 would repeatedly attempt to decode those same bytes without making progress or reading more data from the network.

A malicious server could exploit this behavior to cause excessive CPU usage and prevent the affected request from completing on the client. Network read timeouts would not interrupt the loop because no further socket operation was required.

Affected usages

Applications and libraries using urllib3 versions 2.6.2 through 2.7.0 may be affected when all of the following conditions are met:

  1. Compressed responses from an untrusted source are streamed using HTTPResponse.stream(amt=N) or HTTPResponse.read_chunked(amt=N) with a positive, finite chunk size.
  2. Content decoding is enabled.
  3. The response uses both Transfer-Encoding: chunked and Content-Encoding: deflate.
  4. The decoded body exceeds the requested chunk size and the encoded body contains bytes after the end of the Deflate stream.

HTTPResponse.stream() uses a finite chunk size by default and is therefore affected when the other conditions are met.

Remediation

Upgrade to urllib3 2.8.0, in which the Deflate decoder stops accepting input after reaching the end of the compressed stream and no longer reports trailing bytes as data that can produce more decoded output.

If upgrading is not immediately possible, disable automatic content decoding for responses from untrusted sources by setting decode_content=False, or reject streamed responses using the Deflate content encoding. Applications that disable automatic decoding must handle the compressed response safely at another layer.

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
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "urllib3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.6.2"
            },
            {
              "fixed": "2.8.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-97688"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-30T15:00:38Z",
    "nvd_published_at": "2026-09-29T16:17:18Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nurllib3\u0027s streaming API is designed for the efficient handling of large HTTP responses by reading content in chunks instead of loading the entire response body into memory at once.\n\nurllib3 can decompress response bodies according to the HTTP `Content-Encoding` header. When streaming a compressed, chunked response, urllib3 first consumes data already buffered by the decoder before reading the next HTTP chunk.\n\nHowever, urllib3 versions from 2.6.2 through 2.7.0 could enter an infinite loop when a chunked response contained bytes after the end of the Deflate stream. If the decompressed body exceeded the requested streaming chunk size, Python\u0027s zlib implementation could retain the trailing bytes as unconsumed input after reaching the end of the compressed stream. urllib3 would repeatedly attempt to decode those same bytes without making progress or reading more data from the network.\n\nA malicious server could exploit this behavior to cause excessive CPU usage and prevent the affected request from completing on the client. Network read timeouts would not interrupt the loop because no further socket operation was required.\n\n### Affected usages\n\nApplications and libraries using urllib3 versions 2.6.2 through 2.7.0 may be affected when all of the following conditions are met:\n\n1. Compressed responses from an untrusted source are streamed using `HTTPResponse.stream(amt=N)` or `HTTPResponse.read_chunked(amt=N)` with a positive, finite chunk size.\n2. Content decoding is enabled.\n3. The response uses both `Transfer-Encoding: chunked` and `Content-Encoding: deflate`.\n4. The decoded body exceeds the requested chunk size and the encoded body contains bytes after the end of the Deflate stream.\n\n`HTTPResponse.stream()` uses a finite chunk size by default and is therefore affected when the other conditions are met.\n\n### Remediation\n\nUpgrade to urllib3 2.8.0, in which the Deflate decoder stops accepting input after reaching the end of the compressed stream and no longer reports trailing bytes as data that can produce more decoded output.\n\nIf upgrading is not immediately possible, disable automatic content decoding for responses from untrusted sources by setting `decode_content=False`, or reject streamed responses using the Deflate content encoding. Applications that disable automatic decoding must handle the compressed response safely at another layer.",
  "id": "GHSA-gh4c-6fx4-qh6g",
  "modified": "2026-09-30T15:00:38Z",
  "published": "2026-09-30T15:00:38Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/security/advisories/GHSA-gh4c-6fx4-qh6g"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97688"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/commit/ea2ad7b21a80da3632f80016526a18864586077f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/urllib3/urllib3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/urllib3/urllib3/releases/tag/2.8.0"
    }
  ],
  "schema_version": "1.4.0",
  "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"
    }
  ],
  "summary": "urllib3: Chunked Deflate streaming can enter an infinite loop"
}

GHSA-GH4V-V2HH-G9M6

Vulnerability from github – Published: 2023-03-29 21:30 – Updated: 2023-04-06 15:30
VLAI
Details

This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of Unified Automation OPC UA C++ Demo Server 1.7.6-537 [with vendor rollup]. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of certificates. A crafted certificate can force the server into an infinite loop. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI-CAN-17203.

Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2022-37013"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-835"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2023-03-29T19:15:00Z",
    "severity": "HIGH"
  },
  "details": "This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of Unified Automation OPC UA C++ Demo Server 1.7.6-537 [with vendor rollup]. Authentication is not required to exploit this vulnerability. The specific flaw exists within the handling of certificates. A crafted certificate can force the server into an infinite loop. An attacker can leverage this vulnerability to create a denial-of-service condition on the system. Was ZDI-CAN-17203.",
  "id": "GHSA-gh4v-v2hh-g9m6",
  "modified": "2023-04-06T15:30:18Z",
  "published": "2023-03-29T21:30:20Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-37013"
    },
    {
      "type": "WEB",
      "url": "https://documentation.unified-automation.com/uasdkcpp/1.7.7/CHANGELOG.txt"
    },
    {
      "type": "WEB",
      "url": "https://www.zerodayinitiative.com/advisories/ZDI-22-1029"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

No mitigation information available for this CWE.

No CAPEC attack patterns related to this CWE.

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