Infinite loop in Alt-Svc header parser in hackney_CVE-2026-47066

{
    "lastseen": "",
    "description": "Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in benoitc hackney allows Excessive Allocation. The Alt-Svc response header parser in src/hackney_altsvc.erl does not guarantee forward progress. When parse_token/2 receives a non-token, non-whitespace, non-comma byte (e.g. !, @, =, ;), it returns the input unchanged. skip_comma/1 also returns the buffer unchanged when the first byte is not a comma. parse_entries/2 then recurses with identical data, creating a tight infinite tail-recursive loop that pins a scheduler at 100% CPU. The calling process never returns.\n\nThe entry point parse_and_cache/3 is called synchronously in the connection process on every HTTP response. A single-byte Alt-Svc: ! response header is sufficient to trigger the hang; the header is fully controlled by any HTTP origin the client connects to.\n\nThis issue affects hackney: from 2.0.0-beta.1 before 4.0.1.",
    "published": "2026-05-25T14:00:39.707Z",
    "modified": "2026-05-25T14:00:39.707Z",
    "type": "cve",
    "title": "Infinite loop in Alt-Svc header parser in hackney",
    "source": "EEF",
    "references": "https://github.com/benoitc/hackney/security/advisories/GHSA-6cp8-v795-jr2j\nhttps://cna.erlef.org/cves/CVE-2026-47066.html\nhttps://osv.dev/vulnerability/EEF-CVE-2026-47066\nhttps://github.com/benoitc/hackney/commit/e548aba1f97ffa3f4750da7b772998fb78c01894",
    "id": "CVE-2026-47066",
    "bulletinFamily": "",
    "cwe": [
        "CWE-835"
    ],
    "cvelist": null,
    "sourceData": "benoitc hackney 2.0.0-beta.1\nbenoitc hackney 408e5fe20302226ea8c74dde2bcbd452d712b5b2",
    "sourceHref": "",
    "cvss": {
        "score": 8.7,
        "severity": "HIGH",
        "vector": "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",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "hackney",
    "version": "2.0.0-beta.1",
    "vendor": "benoitc",
    "ai_description": "Infinite loop in Alt-Svc header parser in hackney due to lack of forward progress guarantee, allowing excessive allocation and potential denial-of-service",
    "ai_severity": "High",
    "ai_vendor": "benoitc",
    "ai_product": "hackney",
    "ai_version": "2.0.0-beta.1 to 4.0.0",
    "ai_score": 8.7
}