# CVE-2026-47734: Dulwich uncontrolled memory allocation in git-receive-pack

Source: https://junglewise.ai/threats/cve-2026-47734-dulwich-uncontrolled-memory-allocation-in-git-receive-pack  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-10. Updated: 2026-06-10  
License: CC BY 4.0 with a link back

CVE-2026-47734 · Severity: medium · CVSS 5.7 · Published 2026-06-10

Dulwich is a Python-based library used to implement Git server and client functionality. A vulnerability in how it handles incoming data allows an attacker with push access to crash the server by sending a specially crafted, very small file that triggers massive memory consumption. This can lead to a denial-of-service (DoS) condition, making the Git server unavailable to other users.

Technologies: [dulwich (PyPI)](https://junglewise.ai/threats/technologies/dulwich). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-47734 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47734 being exploited in the wild.

**How severe is CVE-2026-47734?** Medium severity, with a CVSS score of 5.7, published 10 June 2026.

**Which products and versions are affected?** dulwich (PyPI) >= 0.1.0, < 1.2.5, ECOSYSTEM:introduced=0.1.0,fixed=1.2.5.

**Is there a fix for CVE-2026-47734?** Yes. dulwich (PyPI): upgrade to 1.2.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-47734 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-47734?** Check whether you run dulwich (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- dulwich (PyPI): upgrade to 1.2.5 or later

  ```sh
  pip install "dulwich>=1.2.5"
  ```


## Technical details

A memory exhaustion vulnerability (CWE-400/CWE-789) exists in Dulwich's 'add_thin_pack' and 'apply_delta' functions. An attacker with push privileges can submit a small (~174 bytes) crafted thin pack with a delta header declaring an extremely large 'dest_size'. The library attempts to allocate memory based on this attacker-controlled value rather than the actual data received, leading to hundreds of megabytes of allocation. This affects any Dulwich-based Git server exposing 'git-receive-pack', including the HTTP smart server. The issue is fixed in version 1.2.5 by implementing 'max_input_size' checks and honoring the 'receive.maxInputSize' configuration.

## Affected products

- Jelmer Vernooij Dulwich >= 0.1.0, < 1.2.5

## Identifiers

- CVE-2026-47734
- GHSA-xrvj-v92f-53gj
- PYSEC-2026-2466

## Timeline

- 2026-05-28: patched: Version 1.2.5 released
- 2026-05-28: advisory: GitHub Security Advisory published
- 2026-06-10: disclosed: CVE-2026-47734 published to NVD

## References

- [https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5](https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5)
- [https://github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj](https://github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj)

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