CVE-2026-121520
Malicious client could set xattr value outside of BuildKit state directory
In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Malicious client could set xattr value outside of BuildKit state directory
In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.
- Record
CVE-2026-121520- CVSS 4.0
- 4.5 Medium
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H - Weakness
- CWE-61
- Updated
- 2026-11-06
EUVDEUVD-2026-116538
In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.
- Record
EUVD-2026-116538- CVSS 4.0
- 4.5 Medium
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H - Updated
- 2026-11-06
NVD
In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.
- Record
CVE-2026-121520- CVSS 4.0
- 4.5 Medium
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H/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 - Weakness
- CWE-61
- Updated
- 2026-11-06
OSV
Malicious client could set xattr value outside of BuildKit state directory
In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.
- Record
CVE-2026-121520- CVSS 4.0
- 4.5 Medium
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H - Weakness
- CWE-61
- Updated
- 2026-11-07
OSVUBUNTU-CVE-2026-121520
In BuildKit versions prior to v0.34.1, a malicious client with access to the BuildKit control APIs can submit a build request that sets an extended attribute on a file outside the BuildKit state directory. Extended attributes in the trusted. or security. namespaces may also be set, potentially giving a program on the host elevated privileges. This issue affects build services that accept build requests from untrusted users. The issue is fixed in v0.34.1.
- Record
UBUNTU-CVE-2026-121520- CVSS 4.0
- 4.5 Medium
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:H - Updated
- 2026-11-05
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
docker.ioUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 1.6.2~dfsg1-1ubuntu41.10.2-0ubuntu31.10.2-0ubuntu41.10.3-0ubuntu11.10.3-0ubuntu4 Show 19 moreShow less1.10.3-0ubuntu51.10.3-0ubuntu61.11.2-0ubuntu5~16.041.12.1-0ubuntu13~16.04.11.12.3-0ubuntu4~16.04.21.12.6-0ubuntu1~16.04.11.13.1-0ubuntu1~16.04.217.03.2-0ubuntu2~16.04.118.06.1-0ubuntu1~16.04.218.06.1-0ubuntu1.2~16.04.118.09.2-0ubuntu1~16.04.118.09.5-0ubuntu1~16.04.218.09.7-0ubuntu1~16.04.118.09.7-0ubuntu1~16.04.418.09.7-0ubuntu1~16.04.518.09.7-0ubuntu1~16.04.618.09.7-0ubuntu1~16.04.718.09.7-0ubuntu1~16.04.9+esm118.09.7-0ubuntu1~16.04.9+esm2 |
None known |
docker.ioUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 1.13.1-0ubuntu617.03.2-0ubuntu117.03.2-0ubuntu317.03.2-0ubuntu517.12.1-0ubuntu1 Show 22 moreShow less18.06.1-0ubuntu1~18.04.118.06.1-0ubuntu1.2~18.04.118.09.2-0ubuntu1~18.04.118.09.5-0ubuntu1~18.04.218.09.7-0ubuntu1~18.04.118.09.7-0ubuntu1~18.04.318.09.7-0ubuntu1~18.04.419.03.6-0ubuntu1~18.04.119.03.6-0ubuntu1~18.04.219.03.6-0ubuntu1~18.04.320.10.2-0ubuntu1~18.04.220.10.2-0ubuntu1~18.04.320.10.7-0ubuntu1~18.04.120.10.7-0ubuntu1~18.04.220.10.7-0ubuntu5~18.04.220.10.7-0ubuntu5~18.04.320.10.12-0ubuntu2~18.04.120.10.21-0ubuntu1~18.04.220.10.21-0ubuntu1~18.04.320.10.21-0ubuntu1~18.04.3+esm120.10.21-0ubuntu1~18.04.3+esm220.10.21-0ubuntu1~18.04.3+esm3 |
None known |
docker.ioUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 19.03.2-0ubuntu119.03.6-0ubuntu119.03.8-0ubuntu119.03.8-0ubuntu1.20.0419.03.8-0ubuntu1.20.04.1 Show 15 moreShow less19.03.8-0ubuntu1.20.04.220.10.2-0ubuntu1~20.04.220.10.2-0ubuntu1~20.04.320.10.7-0ubuntu1~20.04.120.10.7-0ubuntu1~20.04.220.10.7-0ubuntu5~20.04.120.10.7-0ubuntu5~20.04.220.10.12-0ubuntu2~20.04.120.10.21-0ubuntu1~20.04.120.10.21-0ubuntu1~20.04.220.10.21-0ubuntu1~20.04.420.10.21-0ubuntu1~20.04.520.10.21-0ubuntu1~20.04.620.10.21-0ubuntu1~20.04.6+esm120.10.21-0ubuntu1~20.04.6+esm2 |
None known |
docker.io-appUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 20.10.25-0ubuntu1~20.04.120.10.25-0ubuntu1~20.04.224.0.5-0ubuntu1~20.04.124.0.7-0ubuntu2~20.04.126.1.3-0ubuntu1~20.04.126.1.3-0ubuntu1~20.04.1+esm126.1.3-0ubuntu1~20.04.1+esm2 |
None known |
docker.ioUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 20.10.7-0ubuntu520.10.7-0ubuntu720.10.12-0ubuntu120.10.12-0ubuntu220.10.12-0ubuntu3 Show 11 moreShow less20.10.12-0ubuntu3+gke1.24.120.10.12-0ubuntu420.10.21-0ubuntu1~22.04.220.10.21-0ubuntu1~22.04.320.10.21-0ubuntu1~22.04.520.10.21-0ubuntu1~22.04.620.10.21-0ubuntu1~22.04.720.10.21-0ubuntu1~22.04.7+esm120.10.21-0ubuntu1~22.04.7+esm220.10.21-0ubuntu1~22.04.820.10.21-0ubuntu1~22.04.8+esm1 |
None known |
docker.io-appUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 20.10.25-0ubuntu1~22.04.120.10.25-0ubuntu1~22.04.224.0.5-0ubuntu1~22.04.124.0.7-0ubuntu2~22.04.126.1.3-0ubuntu1~22.04.1 Show 6 moreShow less26.1.3-0ubuntu1~22.04.1+esm127.5.1-0ubuntu3~22.04.127.5.1-0ubuntu3~22.04.228.2.2-0ubuntu1~22.04.129.1.3-0ubuntu3~22.04.129.1.3-0ubuntu3~22.04.2 |
None known |
docker.ioUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 20.10.24+dfsg1-1ubuntu220.10.25+dfsg1-2ubuntu120.10.25+dfsg1-2ubuntu1+esm120.10.25+dfsg1-2ubuntu1+esm220.10.25+dfsg1-2ubuntu1.24.04.120.10.25+dfsg1-2ubuntu1.24.04.1+esm1 |
None known |
docker.io-appUbuntu:Pro:24.04:LTS |
All versions, plus listed versions 24.0.5-0ubuntu124.0.7-0ubuntu124.0.7-0ubuntu224.0.7-0ubuntu324.0.7-0ubuntu4 Show 8 moreShow less24.0.7-0ubuntu4.126.1.3-0ubuntu1~24.04.126.1.3-0ubuntu1~24.04.1+esm127.5.1-0ubuntu3~24.04.127.5.1-0ubuntu3~24.04.228.2.2-0ubuntu1~24.04.129.1.3-0ubuntu3~24.04.129.1.3-0ubuntu3~24.04.2 |
None known |
docker.ioUbuntu:26.10 |
All versions, plus listed versions 27.5.1+dfsg4-2ubuntu128.5.2+dfsg4-5ubuntu1 |
None known |
docker.io-appUbuntu:26.10 |
All versions, plus listed versions 29.1.3-0ubuntu429.1.3-0ubuntu529.1.3-0ubuntu629.7.2-0ubuntu1 |
None known |
docker.ioUbuntu:26.04:LTS |
All versions, plus listed versions 26.1.5+dfsg1-9ubuntu127.5.1+dfsg4-1ubuntu127.5.1+dfsg4-2ubuntu1 |
None known |
docker.io-appUbuntu:26.04:LTS |
All versions, plus listed versions 28.2.2-0ubuntu129.1.2-0ubuntu129.1.3-0ubuntu129.1.3-0ubuntu229.1.3-0ubuntu329.1.3-0ubuntu429.1.3-0ubuntu4.1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, aliases, references | OSV | |
| references | OSV | |
| aliases, references | NVD, OSV | |
| first indexed | CVE List, EUVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-121520 is a medium vulnerability (CVSS 4.5) in Moby Buildkit, published November 3, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.14%, the 3rd percentile. No source names a fixed version.