Dulwich has unbounded memory allocation in receive-pack from crafted thin packs_CVE-2026-47734

{
    "lastseen": "",
    "description": "Dulwich is a pure-Python implementation of the Git file formats and protocols. Starting in version 0.1.0 and prior to version 1.2.5, a client with push access could push a tiny crafted thin pack (~174 bytes)  whose delta header declares a huge   dest_size. When dulwich ingested it via  add_thin_pack / apply_delta, it would  allocate hundreds of MB of memory based on that attacker-controlled size, with no relationship to the actual bytes received. Operators running a Dulwich-based Git server that exposes git-receive-pack (i.e. accepts pushes) - for example via dulwich.server functionality, the HTTP  smart server, or anything built on ReceivePackHandler - are impacted. The issue is patched in 1.2.5. add_thin_pack now accepts a max_input_size keyword (bytes; 0/None = unlimited, matching git's semantics), and ReceivePackHandler reads receive.maxInputSize from the repository config and passes it through. Wire reads are counted and a PackInputTooLarge exception is raised once the cap is exceeded - equivalent to git index-pack --max-input-size. Users should upgrade to Dulwich 1.2.5 or later and set receive.maxInputSize in their server's repository config to a sane bound for their environment. On unpatched versions, receive.maxInputSize has no effect, so it cannot be used as a workaround. Until upgrading, operators should restrict dulwich-receive-pack (push) access to trusted, authenticated clients only, or disable it entirely on servers that only need to serve fetches and/or run the server under an OS-level memory limit (e.g. ulimit, cgroups/MemoryMax, or a container memory limit) so a malicious push is killed rather than taking down the host.",
    "published": "2026-06-10T22:11:02.704Z",
    "modified": "2026-06-10T22:11:02.704Z",
    "type": "cve",
    "title": "Dulwich has unbounded memory allocation in receive-pack from crafted thin packs",
    "source": "GitHub_M",
    "references": "https://github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj\nhttps://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5",
    "id": "CVE-2026-47734",
    "bulletinFamily": "",
    "cwe": [
        "CWE-400",
        "CWE-789"
    ],
    "cvelist": null,
    "sourceData": "jelmer dulwich >= 0.1.0, < 1.2.5",
    "sourceHref": "",
    "cvss": {
        "score": 5.7,
        "severity": "MEDIUM",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
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            "privilegesRequired": "",
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            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "dulwich",
    "version": ">= 0.1.0, < 1.2.5",
    "vendor": "jelmer",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
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    "ai_version": "",
    "ai_score": 0
}