Dulwich has unbounded memory allocation in receive-pack from crafted thin packs

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Summary

CVECVE-2026-47734
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-10 23:16:48 UTC
Updated2026-06-11 15:21:07 UTC
DescriptionDulwich 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.

Risk And Classification

Primary CVSS: v3.1 5.7 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

Problem Types: CWE-400 | CWE-789 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-789 CWE-789: Memory Allocation with Excessive Size Value

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.7MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
3.1CNADECLARED5.7MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Jelmer Dulwich affected >= 0.1.0, < 1.2.5 Not specified

References

ReferenceSourceLinkTags
github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj [email protected] github.com
github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5 [email protected] github.com
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