Security readout for executives and security teams
Plain-English summary
Applications using TOML::XS before 0.06 may crash when processing a deeply nested, untrusted TOML document. The resulting stack overflow can disrupt services that accept attacker-controlled TOML. The bundled parser, tomlc99, is unmaintained; version 0.06 replaces it with tomlc17.
Executive priority
Treat exposed services as an urgent remediation priority because unauthenticated input may cause service failure. Confirm exposure immediately and upgrade vulnerable installations. Prioritize systems receiving TOML through public APIs, uploads, integrations, or automated ingestion; controlled internal-only parsing can follow based on verified reachability.
Technical view
TOML::XS before 0.06 bundles the unsupported tomlc99 parser. Uncontrolled recursion while from_toml processes deeply nested input can exhaust the call stack. Exposure requires attacker-controlled TOML to reach this function. The supplied record rates the issue CVSS 3.1 9.8, although its description specifically documents stack-overflow availability impact.
Likely exposure
Exposure is most likely in network-accessible services, import workflows, or automation that pass untrusted TOML to from_toml. Installations running TOML::XS 0.06 or later are outside the described affected range. Systems parsing only trusted, controlled TOML have lower practical exposure.
Exploitation context
A public tomlc99 issue describes the recursion weakness, but the supplied sources do not establish active exploitation. The CVE is not listed as KEV in the bundle. Exploitation requires supplying sufficiently nested TOML to an application that parses it with a vulnerable TOML::XS version.
Researcher notes
The record associates CWE-1104 and CWE-1395 with reliance on an unmaintained vulnerable component. The described primitive is uncontrolled recursion leading to stack overflow. The supplied CVSS claims high confidentiality, integrity, and availability impacts, but the narrative only substantiates crash risk; broader impact is unconfirmed.
Mitigation direction
- Upgrade TOML::XS to version 0.06 or later.
- Prioritize internet-facing services and workflows accepting externally supplied TOML.
- Until upgraded, prevent untrusted TOML from reaching from_toml.
- Review vendor release notes and guidance before deployment.
Validation and detection
- Inventory installed TOML::XS versions across applications and build artifacts.
- Identify every from_toml call and determine whether its input can be attacker controlled.
- Confirm upgraded deployments resolve TOML::XS 0.06 or later.
- Run existing parser and service regression tests after upgrading.
- Monitor affected services for stack-overflow crashes or abnormal parser terminations.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-1104: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCWE-1395: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-16634 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- Source timelineCPANSec
Version 0.05 released.
- Source timelineCPANSec
The README for tomlc99 was updated to say that it was obsolete.
- Source timelineCPANSec
Vulnerability posted to tomlc99 issue tracker.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- Source timelineCPANSec
Version 0.06 released.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://metacpan.org/release/FELIPE/TOML-XS-0.06/changesCVE reference, CPANSec · release-notes
- https://raw.githubusercontent.com/cktan/tomlc99/29076dfd095bbbbd50a3c1b2760d29f4b83e74ac/README.mdCVE reference, CPANSec
- https://github.com/cktan/tomlc99/issues/97CVE reference, CPANSec · issue-tracking
- https://github.com/cktan/tomlc17CVE reference, CPANSec
- https://toml.io/en/v1.0.0CVE reference, CPANSec · technical-description
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.