# CVE-2026-47734: dulwich: Dulwich is a pure-Python implementation of the Git file formats and protocols

CVE-2026-47734 is fixed in 5 products on 1 platform, first by DEBIAN-CVE-2026-47734, released June 29, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-47734
- Priority: Routine
- CVSS: 5.7 (medium)
- EPSS: 0.0019
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 10, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | dulwich Debian 14 | 1.2.5-1 | [DEBIAN-CVE-2026-47734](https://patchblox.com/security/data/fix/linux/debian-cve-2026-47734.md) | Jun 29, 2026 |
| Linux | python-dulwich-debugsource amzn 2023 | 0.20.18-1.amzn2023.0.3 | [ALAS2023-2026-2026](https://patchblox.com/security/data/fix/linux/alas2023-2026-2026.md) | Aug 3, 2026 |
| Linux | python-dulwich-doc amzn 2023 | 0.20.18-1.amzn2023.0.3 | [ALAS2023-2026-2026](https://patchblox.com/security/data/fix/linux/alas2023-2026-2026.md) | Aug 3, 2026 |
| Linux | python3-dulwich amzn 2023 | 0.20.18-1.amzn2023.0.3 | [ALAS2023-2026-2026](https://patchblox.com/security/data/fix/linux/alas2023-2026-2026.md) | Aug 3, 2026 |
| Linux | python3-dulwich sles 15.7 | 0.20.24-150400.8.1 | [SUSE-SU-2026:2984-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-2984-1.md) | Jul 14, 2026 |
| Linux | python3-dulwich-debuginfo amzn 2023 | 0.20.18-1.amzn2023.0.3 | [ALAS2023-2026-2026](https://patchblox.com/security/data/fix/linux/alas2023-2026-2026.md) | Aug 3, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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