CVE-2026-110676: CWE-405 Asymmetric Resource Consumption (Amplification)
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 software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-110676 affects Cpanel::JSON::XS versions prior to 4.80. The vulnerability arises when the allow_bignum option is enabled, causing JSON numbers with fractions or exponents to decode into Math::BigFloat objects that store the exponent separately, which is efficient. However, when encoding these numbers untyped or as JSON_TYPE_FLOAT, the exponent is expanded into a full decimal representation with one digit per exponent unit, without any bounds. For example, a JSON number like [1e30000000] can expand to 30 MB of text, leading to excessive memory and CPU usage. This asymmetric resource consumption can be triggered by processing untrusted JSON data that is decoded and then encoded again.
Potential Impact
The vulnerability can lead to memory exhaustion and high CPU usage on systems using affected versions of Cpanel::JSON::XS with allow_bignum enabled. This can degrade service availability or cause denial of service conditions due to resource exhaustion. There are no known exploits in the wild at this time.
Mitigation Recommendations
A fix is available in Cpanel::JSON::XS version 4.80 and later. Users should upgrade to version 4.80 or newer to remediate this vulnerability. Until upgraded, avoid enabling allow_bignum when processing untrusted JSON or implement input validation to limit exponent sizes. Patch status is confirmed by the versioning information indicating versions before 4.80 are affected.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- CPANSec
- Date Reserved
- 2026-10-14T13:23:56.248Z
- State
- PUBLISHED
Threat ID: 6ad662ba2cdf04f656803404
Added to database: 10/19/2026, 18:34:34 UTC
Last enriched: 10/19/2026, 18:48:59 UTC
Last updated: 10/19/2026, 22:27:03 UTC
Views: 7
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