Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-2778 is a critical-severity Improper Restriction of Operations within the Bounds of a Memory Buffer (CWE-119) vulnerability in Mozilla Firefox. Its CVSS base score is 10.0 (Critical).
Operationally, ranked at the 49th 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 SA-8 (Security and Privacy Engineering Principles) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-2778 is a sandbox escape vulnerability stemming from incorrect boundary conditions in the DOM: Core & HTML component of Mozilla Firefox and Thunderbird. It affects versions of Firefox prior to 148, Firefox ESR prior to 115.33 and 140.8, and Thunderbird prior to 148 and 140.8. The issue is classified under CWE-119 (improper restriction of operations within the bounds of a memory buffer) with a supporting NVD-CWE-noinfo mapping, and it carries a maximum CVSS v3.1 base score of 10.0.
Remote attackers can exploit this vulnerability over the network with low complexity, requiring no privileges, authentication, or user interaction. The attack vector leverages a changed scope (S:C), enabling high-impact consequences across confidentiality, integrity, and availability (C:H/I:H/A:H). Successful exploitation allows attackers to escape the browser sandbox, potentially granting arbitrary code execution on the host system.
Mozilla's security advisories (MFSA 2026-13 through 2026-16) and the associated Bugzilla entry (bug 2016358) detail the patch deployment in the specified fixed releases. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to mitigate this critical issue, as no workarounds are mentioned in the provided references.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8500
Vulnerability Data
Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
- CWE(s)
Related Threats
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Secure engineering principles require memory-safe design and coding that structurally avoids buffer-boundary violations.
Input validation directly enforces bounds checking that stops out-of-bounds reads/writes from being introduced or reached.
Memory protection restricts exploitation impact of buffer overflows without eliminating the underlying coding flaw.
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.
A.8.25 mandates secure SDLC practices (secure coding guidelines, security requirements, testing including code scans and penetration tests, developer training) that reach buffer management and can stop many buffer overruns from reaching production, but leaves a bounded remainder (e.g. flaws in non-software components, incomplete enforcement of guidelines, or post-deployment changes)
Application security requirements can specify memory-safety rules, but do not prescribe implementation details.
A.8.27 mandates security-by-design principles (e.g. least privilege, fail securely, distrust external input, hardening) plus design reviews that can catch and stop buffer-boundary errors before they reach code, but this is only one minority slice of CWE-119's broad surface (language-specific flaws, unsafe library use, compiler/runtime mitigations, and post-deployment instances remain outside its direct scope).
Secure coding standards explicitly forbid unsafe buffer operations, directly eliminating CWE-119.
Security testing in development catches out-of-bounds accesses before release, covering most instances of the weakness.
Hardening callouts derived
DISA STIG baselines are authored against specific weaknesses. Where this CVE cites a broad weakness class, the mapping is not asserted at that abstraction (owner ruling, 2026-09-25: grade only at Base and below), so no rule is shown here rather than a rule shown against the wrong grain.
- No fine-grained STIG row for CWE-119, a class-level weakness. Rules are authored against its narrower children: CWE-823.