CVE-2021-29136

Host file overwrite via rootfs symlink replacement

Published Apr 6, 2021 · Updated Aug 3, 2024

Path traversal in Open Container Initiative umoci before 0.4.7 allows attackers to overwrite host files through a crafted OCI image. During unpacking, a root entry named "." or "/" can change the rootfs directory into an attacker-controlled symlink, causing later layers to resolve against its host target. Execution of umoci unpack or umoci raw unpack on the image is required, and writes are limited to paths accessible to the invoking account.

CVSS severity5.5
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Open Container Initiative umoci before 0.4.7 allows attackers to overwrite host files through a crafted OCI image. During unpacking, a root entry named "." or "/" can change the rootfs directory into an attacker-controlled symlink, causing later layers to resolve against its host target. Execution of umoci unpack or umoci raw unpack on the image is required, and writes are limited to paths accessible to the invoking account.

The record

CVE
CVE-2021-29136
Published
Apr 6, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, CWE-22, T1565.001
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Apr 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

2.1NIST NVDAV:L/AC:L/Au:N/C:N/I:P/A:N
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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