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.

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.

perl-Cpanel-JSON-XS-4.800.0-1.1 on GA media

Affected: Ubuntu:16.04:LTS: libcpanel-json-xs-perl, Ubuntu:18.04:LTS: libcpanel-json-xs-perl, Ubuntu:20.04:LTS: libcpanel-json-xs-perl, Ubuntu:22.04:LTS: libcpanel-json-xs-perl, Ubuntu:24.04:LTS: libcpanel-json-xs-perl, Ubuntu:26.10: libcpanel-json-xs-perl, Ubuntu:26.04:LTS: libcpanel-json-xs-perl

(Cpanel::JSON::XS versions before 4.80 for Perl allow memory exhaustion ...)