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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48959?
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
Which versions are affected by CVE-2026-48959?
How do I fix CVE-2026-48959?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-48959 being exploited?
There is no known exploitation of CVE-2026-48959 in the wild and no public exploit code.
Sources
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 and 1 more.