# CVE-2026-76845: adm-zip 0.5.9 through 0.6.0 Arbitrary File Overwrite via Symlink Following on Extraction

> Attackers can overwrite arbitrary files outside the extraction directory by exploiting symlink following in adm-zip when overwrite is enabled.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Aug 2026
- **Updated:** 24 Aug 2026
- **Also known as:** CLEANSTART-2026-FG34886, CLEANSTART-2026-RO21037, CLSA-2026-1790457506, GHSA-vwc7-r8mq-g2x9, MINI-236m-6jh4-qq8m, MINI-2j5x-hg3c-22hj, MINI-53wj-fp74-6x48, MINI-6383-v225-3f4q, MINI-882c-qm5c-qm56, MINI-8gf2-52qw-42qr, MINI-9vgg-gr4q-xxc9, MINI-cjjf-289p-cgm5, MINI-gw84-294c-6w74, MINI-h7c4-3w86-xfwv, MINI-j2p5-5hpx-8p99, MINI-p7pp-wwwf-jw3g, MINI-r8j5-9m73-c934, MINI-x45c-3hhm-w8v7

## What is CVE-2026-76845?

CVE-2026-76845 is a medium-severity path traversal vulnerability in cthackers adm-zip, published on 24 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

adm-zip 0.5.9 through 0.6.0 follows symbolic links at the extraction destination. Utils.sanitize in util/utils.js enforces containment by comparing only the string form of an archive entry name against the resolved extraction root, and Utils.writeFileTo opens the computed destination with fs.openSync(path, "w", 0o666), which resolves symbolic links and carries neither O_NOFOLLOW nor a pre-write fs.lstatSync check. When a path component at the destination already exists as a symbolic link pointing outside the extraction root, extractAllTo, extractAllToAsync and extractEntryTo write the entry contents through that link and then chmod its target, placing attacker-controlled content in a file outside the root without any traversal sequence appearing in the archive. Reaching the write requires overwrite to be enabled, because the preceding fs.existsSync check also resolves the link and otherwise declines. An attacker able to create a symbolic link inside a shared, reused or predictable extraction directory, such as a temporary directory or a continuous integration workspace, can overwrite any file the extracting process is permitted to write.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-76845?

2 open source packages ship an affected version, including adm-zip.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `adm-zip` | npm | From 0.5.9 to 0.6.0 | None |
| `adm-zip` | npm | From 0.5.9 to 0.6.0 | None |

## How do I fix CVE-2026-76845?

Upgrade to a fixed version.

## Is CVE-2026-76845 being exploited?

There is no known exploitation of CVE-2026-76845 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-76845 and fix it if it is affected.

What it is: CVE-2026-76845 is a medium-severity path traversal vulnerability in cthackers adm-zip, published on 24 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-76845 in the wild and no public exploit code.

Affected packages and fixed versions:
- adm-zip (npm): affected from 0.5.9 up to 0.6.0; no fix listed
- adm-zip (npm): affected from 0.5.9 up to 0.6.0; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-76845/ (Markdown: https://insights.sbomify.com/CVE-2026-76845/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-76845
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-76845
- OSV: https://osv.dev/vulnerability/CVE-2026-76845

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-76845/
Summaries are generated and may contain mistakes; the official description above is the record.