PT-2026-47590 · Pypi · Dulwich

Published

2026-06-08

·

Updated

2026-06-08

CVSS v3.1

5.7

Medium

VectorAV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

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

Fix

Resource Exhaustion

Weakness Enumeration

CWE-789CWE-400

Related Identifiers

GHSA-XRVJ-V92F-53GJ

Affected Products

Dulwich