PYSEC-2026-2466

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Import Source
https://github.com/pypa/advisory-database/blob/main/vulns/dulwich/PYSEC-2026-2466.yaml
JSON Data
https://api.osv.dev/v1/vulns/PYSEC-2026-2466
Aliases
Published
2026-07-13T15:46:15.665113Z
Modified
2026-07-13T16:31:41.594863437Z
Severity
  • 5.7 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H CVSS Calculator
Summary
Dulwich has unbounded memory allocation in receive-pack from crafted thin packs
Details

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 destsize. When dulwich ingested it via addthinpack / applydelta, 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.

addthinpack now accepts a maxinputsize 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
References

Affected packages

PyPI / dulwich

Package

Name
dulwich
View open source insights on deps.dev
Purl
pkg:pypi/dulwich

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0.1.0
Fixed
1.2.5

Affected versions

0.*
0.1.0
0.1.1
0.2.1
0.3.0
0.3.1
0.3.2
0.3.3
0.4.0
0.4.1
0.5.0
0.6.0
0.6.1
0.6.2
0.7.0
0.7.1
0.8.0
0.8.1
0.8.2
0.8.3
0.8.4
0.8.5
0.8.6
0.8.7
0.9.0
0.9.1
0.9.2
0.9.3
0.9.4
0.9.5
0.9.6
0.9.7
0.9.8
0.9.9
0.10.0
0.10.1a
0.11.0
0.11.1
0.11.2
0.12.0
0.13.0
0.14.0
0.14.1
0.15.0
0.16.0
0.16.1
0.16.2
0.16.3
0.17.1
0.17.2
0.17.3
0.18.0
0.18.1
0.18.2
0.18.3
0.18.4
0.18.5
0.18.6
0.19.0
0.19.1
0.19.2
0.19.3a0
0.19.3
0.19.4
0.19.5
0.19.6
0.19.7
0.19.8
0.19.9
0.19.10
0.19.11
0.19.12
0.19.13
0.19.14
0.19.15
0.19.16
0.20.0
0.20.1
0.20.2
0.20.3
0.20.4
0.20.5
0.20.6
0.20.7
0.20.8
0.20.9
0.20.10
0.20.11
0.20.12
0.20.13
0.20.14
0.20.15
0.20.17
0.20.18
0.20.19
0.20.20
0.20.21
0.20.22
0.20.23
0.20.24
0.20.25
0.20.26
0.20.27
0.20.28
0.20.29
0.20.30
0.20.31
0.20.32
0.20.33
0.20.34
0.20.35
0.20.36
0.20.37
0.20.38
0.20.39
0.20.40
0.20.41
0.20.42
0.20.43
0.20.44
0.20.45
0.20.46
0.20.47
0.20.48
0.20.49
0.20.50
0.21.0
0.21.1
0.21.2
0.21.3
0.21.4
0.21.4.1
0.21.5
0.21.6
0.21.7
0.22.0
0.22.1
0.22.3
0.22.4
0.22.5
0.22.6
0.22.7
0.22.8
0.23.0
0.23.1
0.23.2
0.24.0
0.24.1
0.24.2
0.24.3
0.24.4
0.24.5
0.24.6
0.24.7
0.24.8
0.24.9
0.24.10
0.25.0
0.25.1
0.25.2
1.*
1.0.0
1.1.0
1.2.0
1.2.1
1.2.2
1.2.3
1.2.4

Database specific

source 
"https://github.com/pypa/advisory-database/blob/main/vulns/dulwich/PYSEC-2026-2466.yaml"