# Dulwich infinite loop denial of service in packfile object resolution

Source: https://junglewise.ai/threats/dulwich-infinite-loop-denial-of-service-dos-in-packfile-object-d71acec7  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-02. Updated: 2026-10-02  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 6.5 · Published 2026-10-02

Dulwich is a Git library used by applications to interact with Git repositories. A malicious packfile can trigger an infinite loop in the object resolution code, causing the application to consume 100% CPU and become unresponsive, denying service to legitimate users.

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

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 6.5, published 2 October 2026.

**Which products and versions are affected?** Dulwich <UNKNOWN>; dulwich (PyPI) < 1.2.9.

**Is there a fix for This vulnerability?** No fixed version is recorded yet. Reject OFS_DELTA objects with delta_offset equal to zero, or implement a recursion depth limit (e.g., MAX_DELTA_DEPTH = 50) to prevent long delta chains from causing resource exhaustion.</anigation>
</invoke> If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run Dulwich or 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


Reject OFS_DELTA objects with delta_offset equal to zero, or implement a recursion depth limit (e.g., MAX_DELTA_DEPTH = 50) to prevent long delta chains from causing resource exhaustion.</anigation>
</invoke>

## Technical details

The vulnerability exists in the `Pack.resolve_object` method when resolving OFS_DELTA objects. If delta_offset is zero, the calculation `base_offset = obj_offset - delta_offset` creates a self-referential offset that points back to the current object. Without depth tracking or validation, this causes infinite recursion. An attacker can craft a malicious packfile with a zero delta_offset to trigger this condition.

## Affected products

- Dulwich Dulwich <UNKNOWN>

## Timeline

- 2026-10-02: disclosed

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