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Vulnerability · Published Oct 19, 2026 · Assigned by CPANSec

CVE-2026-110676Cpanel::JSON::XS versions before 4.80 for Perl allow memory exhaustion by encoding exponent notation as full decimal digits under allow_bignum

High 7.5

In plain English

A high-severity security flaw in Cpanel-JSON-XS. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.5%top 58.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Cpanel::JSON::XS versions before 4.80 for Perl allow memory exhaustion by encoding exponent notation as full decimal digits under allow_bignum. With allow_bignum, a JSON number with a fraction or exponent decodes to a Math::BigFloat, which stores the exponent separately and so decodes cheaply. Encoding it untyped or as JSON_TYPE_FLOAT writes the plain decimal form with one digit per unit of exponent. Nothing bounds the exponent, so the 12-byte text [1e30000000] encodes to 30 MB. Untrusted JSON decoded with allow_bignum and encoded again can exhaust memory and CPU.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12libcpanel-json-xs-perlno fix listedDEBIAN-CVE-2026-110676
Debian:13libcpanel-json-xs-perlno fix listedDEBIAN-CVE-2026-110676
Debian:14libcpanel-json-xs-perl4.80-1DEBIAN-CVE-2026-110676
Ubuntu:22.04:LTSlibcpanel-json-xs-perlno fix listedUBUNTU-CVE-2026-110676
Ubuntu:24.04:LTSlibcpanel-json-xs-perlno fix listedUBUNTU-CVE-2026-110676
Ubuntu:26.04:LTSlibcpanel-json-xs-perlno fix listedUBUNTU-CVE-2026-110676
Ubuntu:26.10libcpanel-json-xs-perlno fix listedUBUNTU-CVE-2026-110676

Affected products (as reported)

VendorProductVersions
Cpanel-JSON-XS 0 – before 4.80

Weakness: CWE-405 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References