Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:NSummary
CVE-2026-49859 is a medium-severity Protection Mechanism Failure (CWE-693) vulnerability in Deno Deno. Its CVSS base score is 5.2 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Abuse Elevation Control Mechanism (T1548); ranked at the 1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and AC-4 (Information Flow Enforcement) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-38541
Vulnerability Data
Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.1, when fetch() was called, Deno checked the destination hostname against --deny-net rules but did not re-check the IP addresses that hostname resolved to. An attacker-controlled script could use a…
more
specially crafted domain name that passes the hostname check yet resolves to a denied IP, bypassing the network restriction entirely. This vulnerability is fixed in 2.8.1.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 8 hardening rules · 6 OS baselines
V6.3.3V6.6.3V10.2.2V1.3.6
Mitigating Controls (NIST 800-53 r5) AI
AC-3 directly requires enforcement of access authorizations via the protection mechanism itself.
AC-4 mandates use of information flow enforcement mechanisms to control data movement.
SC-2 requires separation of user and system functionality as a protection mechanism.
SC-28 requires protection mechanisms for information at rest.
SC-3 requires isolation of security functions from non-security functions.
SC-7 requires boundary protection mechanisms to monitor and control external communications.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Enforcing authentication directly implements a core protection mechanism whose absence or misuse is the CWE.
Defining and enforcing access authorizations is a protection mechanism; proper use prevents the CWE.
Cryptographic and integrity controls are protection mechanisms whose correct deployment mitigates the CWE.
Encryption and integrity protections for transit are explicit protection mechanisms.
Logical network protections are protection mechanisms whose failure matches the CWE.
Secure development practices directly include input validation and destination allow-listing that prevent SSRF.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Systematic verification that security mechanisms operate according to defined standards reduces the likelihood that protection mechanisms are bypassed or disabled.
Operational threat data describing SSRF campaigns can be used to tighten outbound-request allow-lists and detection rules before attackers exploit them.
Hardening devices, disabling vulnerable protocols, and maintaining accurate network diagrams reduce the likelihood that a protection mechanism is misconfigured or left in a weak state.
Requiring defined escalation paths, crisis activation criteria, and coordination procedures strengthens the overall protection mechanism so that a single control failure is less likely to leave the organization exposed.
By requiring a documented categorization and decision process for security events, the control ensures that protection mechanisms are not bypassed or ignored when anomalies occur.
Identifying and remediating control weaknesses that contributed to an incident reduces the likelihood that protection mechanisms will fail again.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248524 OL 8 must implement NIST FIPS-validated cryptography for the following: To provision digital signatures, to generate cryptographic hashes, and to protect data requiring data-at-rest protections in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards. prevents CWE-693
- V-248525 All OL 8 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at-rest protection. prevents CWE-693
Windows 10 (2 rules)
- V-220865 The Windows Remote Management (WinRM) service must not use Basic authentication. prevents CWE-693
- V-220812 Credential Guard must be running on Windows 10 domain-joined systems. prevents CWE-693
Windows 11 (1 rule)
- V-253418 The Windows Remote Management (WinRM) service must not use Basic authentication. prevents CWE-693
Windows Server 2016 (1 rule)
- V-225012 Windows Server 2016 must be running Credential Guard on domain-joined member servers. prevents CWE-693
Windows Server 2019 (1 rule)
- V-205907 Windows Server 2019 must be running Credential Guard on domain-joined member servers. prevents CWE-693
Windows Server 2022 (1 rule)
- V-254441 Windows Server 2022 must be running Credential Guard on domain-joined member servers. prevents CWE-693