Raw vector
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2026-1979 is a medium-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Mruby Mruby. Its CVSS base score is 4.8 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 5th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SI-16 (Memory Protection) and SI-2 (Flaw Remediation) — see the control section below for these in your framework.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-5583
Vulnerability Data
A flaw has been found in mruby up to 3.4.0. This affects the function mrb_vm_exec of the file src/vm.c of the component JMPNOT-to-JMPIF Optimization. Executing a manipulation can lead to use after free. The attack needs to be launched locally.…
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The exploit has been published and may be used. This patch is called e50f15c1c6e131fa7934355eb02b8173b13df415. It is advisable to implement a patch to correct this issue.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Local UAF memory corruption in mruby VM enables code execution for privilege escalation.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
- 3 hardening rules · 3 OS baselines
V17.3.2V1.4.3
Mitigating Controls (NIST 800-53 r5) AI
Directly requires applying the published patch (e50f15c) that eliminates the JMPNOT-to-JMPIF use-after-free in mrb_vm_exec.
Enforces memory-protection mechanisms that block use-after-free exploitation in the mruby VM.
Requires integrity checks on mruby bytecode and VM state to detect or block manipulation that triggers the CWE-416 flaw.
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.
Secure SDLC practices (bounds checking, safe APIs, reviews) directly prevent this class of flaw.
Vulnerability scanning and code analysis directly surface buffer-boundary flaws.
Receiving and triaging vulnerability disclosures commonly includes buffer-related reports.
Developer training on secure coding reduces introduction of memory-buffer errors.
Patching replaces vulnerable code containing buffer-boundary defects.
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.
Security testing in development catches out-of-bounds accesses before release, covering most instances of the weakness.
Secure development lifecycle mandates memory-safety practices that directly prevent buffer-boundary violations.
Application security requirements can specify memory-safety rules, but do not prescribe implementation details.
Secure architecture and engineering principles include memory-safe design patterns that mitigate buffer overflows.
Secure coding standards explicitly forbid unsafe buffer operations, directly eliminating CWE-119.
Change-management processes help ensure memory-safety fixes are deployed consistently.