BREW-CONDA-LOCK-CVE-2026-47734 (GHSA-XRVJ-V92F-53GJ)
Vulnerability from osv_homebrew – Published: 2026-08-13 16:41 – Updated: 2026-09-09 23:48 – Source websiteImpact
An uncontrolled-resource-consumption (memory exhaustion) denial-of-service vulnerability (CWE-400 / CWE-789).
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.
Who is impacted: 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.
Patches
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.
Workarounds
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.
- 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.
Resources
- git's receive.maxInputSize / git index-pack --max-input-size documentation
- Reported by Liyi, Ziyue, Strick, Maurice and Chenchen @ University of Sydney
{
"affected": [
{
"ecosystem_specific": {
"fix": null,
"range_state": "affected",
"resource": "dulwich",
"resource_purl": "pkg:pypi/dulwich@0.24.10",
"upstream_fixed_in": "1.2.5"
},
"package": {
"ecosystem": "Homebrew",
"name": "conda-lock",
"purl": "pkg:brew/conda-lock"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"database_specific": {
"confidence": "high",
"source": "matched",
"strategy": "registry",
"upstream_evidence": [
{
"ecosystem": "PyPI",
"key": "pkg:pypi/dulwich@0.24.10",
"name": "dulwich",
"resource": "dulwich",
"strategy": "registry",
"subject_version": "0.24.10"
}
]
},
"details": "## Impact\n\nAn uncontrolled-resource-consumption (memory exhaustion) denial-of-service vulnerability (CWE-400 / CWE-789).\n\nA 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.\n\nWho is impacted: Operators running a Dulwich-based Git server that exposes git-receive-pack (i.e. accepts pushes) -\nfor example via dulwich.server functionality, the HTTP smart server, or anything built on ReceivePackHandler. \n\n## Patches\n\nPatched in 1.2.5.\n\nadd_thin_pack now accepts a max_input_size keyword (bytes; 0/None = unlimited, matching git\u0027s 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.\n\nUsers should upgrade to Dulwich 1.2.5 or later and set receive.maxInputSize in their server\u0027s repository config to a sane bound for their environment.\n\n## Workarounds\n\nOn unpatched versions, receive.maxInputSize has no effect, so it cannot be used as a workaround. Until upgrading, operators should:\n\n- Restrict dulwich-receive-pack (push) access to trusted, authenticated clients only, or disable it entirely on servers that only need to serve fetches.\n- 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.\n\n## Resources\n\n- git\u0027s receive.maxInputSize / git index-pack --max-input-size documentation \n- Reported by Liyi, Ziyue, Strick, Maurice and Chenchen @ University of Sydney",
"id": "BREW-conda-lock-CVE-2026-47734",
"modified": "2026-09-09T23:48:38Z",
"published": "2026-08-13T16:41:05Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-47734"
},
{
"type": "PACKAGE",
"url": "https://github.com/jelmer/dulwich"
},
{
"type": "WEB",
"url": "https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5"
}
],
"schema_version": "1.7.3",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "Dulwich has unbounded memory allocation in receive-pack from crafted thin packs",
"upstream": [
"GHSA-xrvj-v92f-53gj",
"CVE-2026-47734",
"PYSEC-2026-2466"
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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- Published Proof of Concept: A public proof of concept is available for this vulnerability.
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- 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.
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