Vulnerability in github.com/opencontainers/umoci (CVE-2021-29136)
Summary
Vulnerability in github.com/opencontainers/umoci (CVE-2021-29136). Data can be tampered with by attackers. Mitigation: upgrade to 0.4.7 or later.
Original description
The description as published by the source.
Impact
umoci 0.4.6 and earlier can be tricked into modifying host files by
creating a malicious layer that has a symlink with the name "." (or
"/"). Because umoci deletes inodes if they change types, this results in
the rootfs directory being replaced with an attacker-controlled symlink.
Subsequent image layers will then be applied on top of the target of the
symlink (which could be any directory on the host filesystem the user
running umoci has access to).
While umoci does have defences against symlink-based attacks, they are
all implemented by resolving things relative to the rootfs directory --
if the rootfs itself is a symlink, umoci resolves it first.
This vulnerability affects both "umoci unpack" and "umoci raw unpack".
Patches
This issue has been patched in umoci 0.4.7, see the references section
for the specific commit which fixed this vulnerability.
Workarounds
Note that if you use umoci as an unprivileged user (using the --rootless
flag) then umoci will not be able to overwrite any files that your user
doesn't have access to. Other possible mitigations are to run umoci
under an LSM profile such as AppArmor or SELinux to restrict the level
of access it has outside of container image directories.
References
Credits
Thanks to Robin Peraglie from Cure53 f…
Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2021-29136 has been found in github.com/opencontainers/umoci.
Data can be tampered with by attackers.
What to do: upgrade github.com/opencontainers/umoci to 0.4.7 or later.
If unsure, ask your IT team or search "github.com/opencontainers/umoci CVE-2021-29136" on the vendor's site.
CVE-2021-29136 (github.com/opencontainers/umoci) — CWE-20
Attack vector: local / no user interaction
Patched: 0.4.7 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-20) exists in github.com/opencontainers/umoci.
Check the vendor advisory for the affected versions of github.com/opencontainers/umoci.
Severity: ?. Data can be tampered with by attackers.
Update to 0.4.7.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/opencontainers/umoci' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'github.com/opencontainers/umoci' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/opencontainers/umociを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade github.com/opencontainers/umoci to 0.4.7ステージング環境で 0.4.7 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- web github.com
- web github.com
- web openwall.com