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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-73639?
How do I fix CVE-2026-73639?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-73639 being exploited?
There is no known exploitation of CVE-2026-73639 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-73639, GHSA-jhx5-34j8-9g88, UBUNTU-CVE-2026-73639.