CVE-2026-129113JSON-XS integer underflow
CVE-2026-129113 is a integer underflow in JSON-XS, not yet scored.
Why this priority: Not scored yet, and no exploitation signal.
Published · Updated · NVD status: Received
What it is
A subtraction wraps below zero and produces a huge value used as a size or index.
How it is reached
The record does not say yet how the flaw is reached; the description below is the best guide until it is scored.
What an attacker gains
Its impact has not been scored yet. In practice, this kind of flaw lets an attacker crash the process, read memory, or in the worst case run code.
Is it being exploited?
There is no public report of exploitation yet.
What to do
- Upgrade JSON-XS to 4.05 or later.
Description from NVD
JSON::XS versions from 4.0_00 before 4.05 for Perl corrupt the incremental buffer length by chopping past its end in incr_skip after a top-level number.
The incremental parser scans any run of digits, signs, dots and exponent markers as one number, but the decoder stops at the end of a valid number, so the parser keeps an offset into bytes it has not decoded. It then empties the buffer without clearing those bytes, and a later incr_parse call without new input reads them again and moves the offset past the end of the buffer. incr_skip, the documented recovery after an error, removes that many bytes and the buffer length wraps.
A peer sending input such as "1-2" to an incr_parse consumer can make the next read of incr_text exit the process through perl's uncatchable out-of-memory path.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Native code: operating systems, browsers and firmware. The flaw sits wherever native code reads untrusted data.
- Network appliances and media or file parsers. The flaw sits wherever native code reads untrusted data.
Trust boundaries in play
- Wherever native code reads untrusted data. An attacker who crosses it can crash the process, read memory, or in the worst case run code.
Questions to answer about your own systems
- Where does JSON-XS run in your systems, and at which version?
- Which of those instances are reachable by people you do not trust?
- What can it reach once compromised: which data stores, secrets and services?
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.