# CVE-2026-48959: IO::Uncompress::Unzip versions before 2.220 for Perl allow CPU exhaustion via per-byte read loop in fastForward

> An attacker can cause CPU exhaustion in Perl applications using IO::Uncompress::Unzip by providing a malicious zip file, leading to denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 May 2026
- **Updated:** 29 May 2026
- **Also known as:** AZL-89307, BELL-CVE-2026-48959, DEBIAN-CVE-2026-48959, ECHO-c2dc-1c4d-e477, GHSA-7vxx-5gqr-7r44, ROOT-OS-DEBIAN-11-CVE-2026-48959, UBUNTU-CVE-2026-48959

## What is CVE-2026-48959?

CVE-2026-48959 is a high-severity denial of service vulnerability in PMQS IO::Uncompress::Unzip, published on 27 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

IO::Uncompress::Unzip versions before 2.220 for Perl allow CPU exhaustion via per-byte read loop in fastForward.

fastForward() compares length $offset (the digit count of the offset, 1 to 19) against the chunk size $c instead of $offset itself, so $c shrinks from 16 KiB to 1-19 bytes per iteration.

Extracting a named entry from an attacker supplied zip via IO::Uncompress::Unzip->new($zip, Name => $target) drives a per-byte read loop scaling with the entry's compressed size, up to the non-Zip64 4 GiB cap.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-48959?


## How do I fix CVE-2026-48959?

Upgrade to a fixed version.

## Is CVE-2026-48959 being exploited?

There is no known exploitation of CVE-2026-48959 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48959 and fix it if it is affected.

What it is: CVE-2026-48959 is a high-severity denial of service vulnerability in PMQS IO::Uncompress::Unzip, published on 27 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-48959 in the wild and no public exploit code.

Affected product: PMQS IO::Uncompress::Unzip. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-48959/ (Markdown: https://insights.sbomify.com/CVE-2026-48959/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48959
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48959
- OSV: https://osv.dev/vulnerability/CVE-2026-48959

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48959/
Summaries are generated and may contain mistakes; the official description above is the record.