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CVE-2026-122299

Dulwich before 1.2.20 Commit Parser Tree Header Misinterpretation

8.6 High

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Active

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

0.33%Unchanged since Nov 5, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.6

Dulwich before 1.2.20 Commit Parser Tree Header Misinterpretation

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
CVE-2026-122299
CVSS 4.0
8.6 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-1250, CWE-115
Updated
2026-11-04
EUVDEUVD-2026-117194 8.6

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
EUVD-2026-117194
CVSS 4.0
8.6 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Updated
2026-11-05
GitHub AdvisoriesGHSA-6jv4-m4h7-2vv8 8.6

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in...

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
GHSA-6jv4-m4h7-2vv8
CVSS 4.0
8.6 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-115
Updated
2026-11-05
NVD 8.6

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
CVE-2026-122299
CVSS 4.0
8.6 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-115, CWE-1250
Updated
2026-11-05
OSV 8.6

Dulwich before 1.2.20 Commit Parser Tree Header Misinterpretation

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
CVE-2026-122299
CVSS 4.0
8.6 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Weakness
CWE-115, CWE-1250
Updated
2026-11-05
OSVDEBIAN-CVE-2026-122299 8.8

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
DEBIAN-CVE-2026-122299
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-05
OSVUBUNTU-CVE-2026-122299 8.6

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
UBUNTU-CVE-2026-122299
CVSS 4.0
8.6 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CVSS 3.1
8.8 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Updated
2026-11-06
OSVAZL-112720 No score

CVE-2026-122299 affecting package python-dulwich 0.21.7-6

Dulwich before 1.2.20 contains a commit object parsing vulnerability where the read path in _parse_commit resolves a duplicate tree header to the last occurrence instead of the first, diverging from core git's resolution behavior, while Poetry 2.5.1 ships this version and uses dulwich by default for git dependency installation. Attackers can craft a commit object with two tree headers so that reviewers and CI using git see a benign tree while Poetry's dulwich-based checkout resolves to a different attacker-controlled tree containing malicious build scripts such as setup.py, resulting in unreviewed code execution on the install or build host.

Record
AZL-112720
Updated
2026-11-07

Affected products

Affected packages

Affected packages
PackageAffectedFixed
python-dulwich
Azure Linux:3
through 0.21.7-6 None known
dulwich
Debian:12
All versions, plus listed versions
0.21.2-10.21.5-10.21.6-10.22.5-10.22.7-1
Show 17 moreShow less
0.22.7-20.24.10-10.24.2-10.24.2-21.0.0-11.0.0-21.1.0-11.1.0-21.1.0-31.2.0-11.2.1-11.2.11-11.2.12-11.2.17-11.2.5-11.2.7-11.2.7-2
None known
dulwich
Debian:13
All versions, plus listed versions
0.22.7-10.22.7-20.24.10-10.24.2-10.24.2-2
Show 13 moreShow less
1.0.0-11.0.0-21.1.0-11.1.0-21.1.0-31.2.0-11.2.1-11.2.11-11.2.12-11.2.17-11.2.5-11.2.7-11.2.7-2
None known
dulwich
Debian:14
All versions, plus listed versions
0.22.7-10.22.7-20.24.10-10.24.2-10.24.2-2
Show 13 moreShow less
1.0.0-11.0.0-21.1.0-11.1.0-21.1.0-31.2.0-11.2.1-11.2.11-11.2.12-11.2.17-11.2.5-11.2.7-11.2.7-2
None known
dulwich
Ubuntu:16.04:LTS
All versions, plus listed versions
0.11.2-1ubuntu10.12.0-10.12.0-1build10.12.0-1build2
None known
dulwich
Ubuntu:18.04:LTS
All versions, plus listed versions
0.18.2-1build10.18.5-1
None known
dulwich
Ubuntu:20.04:LTS
All versions, plus listed versions
0.19.11-20.19.14-4ubuntu10.19.15-10.19.15-1build1
None known
dulwich
Ubuntu:22.04:LTS
All versions, plus listed versions
0.20.15-1ubuntu10.20.31-1ubuntu10.20.31-1.10.20.31-1.1build1
None known
dulwich
Ubuntu:24.04:LTS
All versions, plus listed versions
0.21.6-10.21.6-1build10.21.6-1build2
None known
dulwich
Ubuntu:26.10
All versions, plus listed versions
1.1.0-31.2.12-1
None known
dulwich
Ubuntu:26.04:LTS
All versions, plus listed versions
0.22.7-10.24.2-21.1.0-2ubuntu11.1.0-3
None known

History

History
RecordedChangedSources
affected, aliases, referencesOSV
affected, aliases, referencesOSV
affected, aliases, referencesOSV
referencesOSV
publishedEUVD, NVD
aliases, publishedEUVD
aliases, referencesGitHub Advisories
first indexedCVE List

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-122299 is a high vulnerability (CVSS 8.6) in Jelmer Dulwich, published November 4, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.33%, the 25th percentile. No source names a fixed version.

References

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