CVE-2026-9516 Denial of service in Cpanel::JSON::XS
Attackers can crash Perl applications using Cpanel::JSON::XS by sending UTF-8 BOM prefixed JSON that triggers a filter callback exception.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-9516?
CVE-2026-9516 is a high-severity denial of service vulnerability in RURBAN Cpanel::JSON::XS, published on 3 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Cpanel::JSON::XS versions before 4.41 for Perl allow denial of service via UTF-8 BOM prefixed input when a decode filter callback throws.
To skip a leading 3-byte UTF-8 BOM, decode_json() advances the input scalar's string pointer past the mark with SvPV_set() and restores it only on the normal return path. When decoding aborts through a Perl exception, for example a filter_json_object callback that croaks, the restore is skipped and the scalar is left with its string pointer offset into its own buffer and a shortened length.
When that scalar is later freed, the allocator receives an invalid pointer and the interpreter aborts. A single BOM prefixed document decoded with a throwing filter callback crashes any caller.
Which versions are affected by CVE-2026-9516?
It affects 1 product.
Products include Rurban Cpanel\.
How do I fix CVE-2026-9516?
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-2026-9516 being exploited?
There is no known exploitation of CVE-2026-9516 in the wild and no public exploit code.
Other vulnerabilities in RURBAN Cpanel::JSON::XS
Sources
Also known as AZL-89399, DEBIAN-CVE-2026-9516, GHSA-32gp-2g42-v9vc, UBUNTU-CVE-2026-9516.