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Uncontrolled Resource ConsumptionWeakness · CWE-400

CVE-2026-47734

MEDIUM · 5.7 CVSS v3.1 Published 2026-06-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
61/100
Remediation priority · Elevated
Remotely reachable

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Dulwich Git server versions prior to 1.2.5 are vulnerable to memory exhaustion via crafted thin packs. Attackers can push malicious packs where delta headers declare huge dest_size values (~hundreds of MB) while only sending ~174 bytes, causing the server to allocate excessive memory based on attacker-controlled values.

MitigationUpgrade to Dulwich 1.2.5 or later and configure receive.maxInputSize in repository config to limit pack input size. Until patched, restrict push access to trusted clients or apply OS-level memory limits.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if Dulwich Git server is in use
    Check for running Python processes that import dulwich modules, or search for server configuration files that reference 'dulwich' in project dependencies (e.g., requirements.txt, setup.py, pyproject.toml)
    Affected if Dulwich is installed and used as a Git server component
  2. Determine installed Dulwich version
    Run 'pip show dulwich' or 'python -c "import dulwich; print(dulwich.__version__)"' to obtain the version number
    Affected if Version is earlier than 1.2.5 (the fixed release)
  3. Verify push access is enabled
    Inspect the Dulwich server configuration or application code that initializes the Git server; look for instances of 'git_receive_pack' or push-related handlers being registered
    Affected if Push access is enabled and accessible to untrusted or external clients
  4. Check receive.maxInputSize configuration
    Inspect repository configuration files (e.g., .git/config within served repositories) or server-side configuration for the 'receive.maxInputSize' setting
    Affected if maxInputSize is not set or is set to an extremely large value, providing no effective bound on pack input

A user is affected if they run Dulwich versions prior to 1.2.5 as a Git server with push access enabled and without an effective maxInputSize limit configured.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to Dulwich 1.2.5 or later and configure receive.maxInputSize in repository config to limit pack input size. Until patched, restrict push access to trusted clients or apply OS-level memory limits.

Recommended fix High confidence

Dulwich 1.2.5

  1. Upgrade to Dulwich version 1.2.5 or later
  2. After upgrading, configure receive.maxInputSize in the repository config to a sane bound for your environment (e.g., add '[receive] maxInputSize = 524288000' for 500MB limit)

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,570
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-47734 in production — separate from our analysis above.

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What this is

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