---
id: CVE-2026-47734
aliases:
  - GHSA-xrvj-v92f-53gj
title: >-
  Dulwich has unbounded memory allocation in receive-pack from crafted thin
  packs
summary: >-
  Dulwich has unbounded memory allocation in receive-pack from crafted thin
  packs
severity: medium
cvss: 5.7
cwe:
  - CWE-400
  - CWE-789
vendor: dulwich
product: dulwich
ecosystem: pip
affected:
  - 'dulwich >= 0.1.0, < 1.2.5'
patched:
  - dulwich 1.2.5
published: '2026-06-08'
updated: '2026-06-11'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-xrvj-v92f-53gj'
references:
  - url: 'https://github.com/jelmer/dulwich/security/advisories/GHSA-xrvj-v92f-53gj'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-47734'
  - url: 'https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.5'
  - url: 'https://github.com/advisories/GHSA-xrvj-v92f-53gj'
tags:
  - ghsa
  - pip
epss: 0.00188
epssPercentile: 0.08674
ingestedAt: '2026-07-07T15:41:59.614Z'
---

## Overview

## Impact

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 packages

- `dulwich >= 0.1.0, < 1.2.5`

## Remediation

Upgrade to a patched release:

- `dulwich 1.2.5`