# CVE-2026-73639: Imager::File::PNG versions from 1.003 before 1.004 for Perl write past the end of the row buffer reading a PNG with a tRNS transparency chunk in read_direct8.

> A heap buffer overflow in the Perl Imager PNG reader allows attackers to crash the application by supplying a malicious PNG file with a tRNS chunk.

- **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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:** 17 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-73639, GHSA-jhx5-34j8-9g88, UBUNTU-CVE-2026-73639

## What is CVE-2026-73639?

CVE-2026-73639 is a critical memory corruption vulnerability, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Imager::File::PNG versions from 1.003 before 1.004 for Perl write past the end of the row buffer reading a PNG with a tRNS transparency chunk in read_direct8.

With a tRNS chunk, read_direct8() adds an alpha channel to the image it creates but still sizes the row buffer from the original channel count. libpng expands the transparency into that extra channel, so png_read_row() fills one channel more than the buffer holds, at one byte per sample, and writes width bytes past the end of the allocation. Palette images go to read_paletted() and 16-bit images to read_direct16(), which sizes its buffer from png_get_rowbytes() and allocates enough for the expanded row.

The same reader ships bundled in the Imager distribution.

Reading an attacker-supplied PNG through Imager->read() corrupts the heap, which can crash the process.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-73639?


## How do I fix CVE-2026-73639?

Upgrade to a fixed version.

## Is CVE-2026-73639 being exploited?

There is no known exploitation of CVE-2026-73639 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-73639 and fix it if it is affected.

What it is: CVE-2026-73639 is a critical memory corruption vulnerability, published on 17 Sep 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-2026-73639 in the wild and no public exploit code.

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-2026-73639/ (Markdown: https://insights.sbomify.com/CVE-2026-73639/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-73639
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-73639
- OSV: https://osv.dev/vulnerability/CVE-2026-73639

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-73639/
Summaries are generated and may contain mistakes; the official description above is the record.