CVE-2026-56017 Null dereference in JavaScript::Minifier::XS
A remote attacker can crash a service using this Perl library by sending JavaScript input starting with a slash, causing a 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-2026-56017?
CVE-2026-56017 is a high-severity vulnerability in GTERMARS JavaScript::Minifier::XS, published on 29 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
JavaScript::Minifier::XS versions before 0.16 for Perl crash with a NULL pointer dereference when the first meaningful token of the input is a slash.
The regexp versus division disambiguator in JsTokenizeString (XS.xs) inspects the previous token's last byte to choose between a regexp literal and a division operator. When a slash is the first meaningful token, with the start of input or only whitespace and comments before it, there is no valid preceding token: the walk back over whitespace and comment nodes runs off the head of the node list to NULL, and the byte lookup reads through a NULL contents pointer at an underflowed length index. The following identifier check dereferences the same NULL pointer.
The crash is reachable through the public minify() API, so input as small as a single slash byte crashes the calling process. A service that minifies untrusted or third-party JavaScript can be crashed by a remote request, causing denial of service.
Which versions are affected by CVE-2026-56017?
How do I fix CVE-2026-56017?
Upgrade to a fixed version.
Is CVE-2026-56017 being exploited?
There is no known exploitation of CVE-2026-56017 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-56017, DEBIAN-CVE-2026-56017, GHSA-72fp-jmq3-p5xj, UBUNTU-CVE-2026-56017.