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.
Project Subscriptions
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Advisories
| Source | ID | Title |
|---|---|---|
Github GHSA |
GHSA-xrvj-v92f-53gj | Dulwich has unbounded memory allocation in receive-pack from crafted thin packs |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Wed, 10 Jun 2026 22:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | Dulwich has unbounded memory allocation in receive-pack from crafted thin packs | |
| Weaknesses | CWE-400 CWE-789 |
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| References |
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| Metrics |
cvssV3_1
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Projects
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-06-10T22:11:02.704Z
Reserved: 2026-05-19T22:16:39.503Z
Link: CVE-2026-47734
No data.
Status : Received
Published: 2026-06-10T23:16:48.807
Modified: 2026-06-10T23:16:48.807
Link: CVE-2026-47734
No data.
OpenCVE Enrichment
Updated: 2026-06-10T23:30:44Z
Github GHSA