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CVE-2026-8388 Mozilla CVE debrief

CVE-2026-8388 is a medium-severity vulnerability (CVSS 6.5) in Mozilla's JavaScript Engine: JIT component, caused by incorrect boundary conditions. The vulnerability was published on May 12, 2026, and last modified on May 19, 2026. It affects Firefox versions prior to 150.0.3, Firefox ESR versions prior to 115.36 and 140.11, and Thunderbird versions prior to 140.11. The weakness is classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer). Mozilla has released security advisories addressing this issue across multiple product lines.

Vendor
Mozilla
Product
Firefox
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-12
Original CVE updated
2026-07-15
Advisory published
2026-05-12
Advisory updated
2026-07-15

Who should care

Organizations running Mozilla Firefox, Firefox ESR, or Thunderbird in desktop environments should prioritize patching, particularly those with users accessing untrusted web content. Security teams should verify patch deployment across managed endpoints and consider additional mitigations such as content filtering or application control for high-risk user populations until updates are confirmed.

Technical summary

This vulnerability stems from incorrect boundary conditions in the Just-In-Time (JIT) compiler component of Mozilla's JavaScript engine. JIT compilers dynamically compile JavaScript to native machine code for performance optimization. Boundary condition errors in this context typically involve improper validation of array indices, buffer sizes, or memory access ranges during the compilation or execution of optimized code paths. The CVSS scoring reflects network accessibility and low attack complexity, suggesting potential for remote exploitation through malicious web content. The confidentiality and integrity impacts (C:L/I:L) with no availability impact (A:N) suggest information disclosure or limited code execution scenarios rather than system-wide compromise.

Defensive priority

medium

Recommended defensive actions

  • Upgrade Firefox to version 150.0.3 or later
  • Upgrade Firefox ESR to version 115.36 or 140.11 or later
  • Upgrade Thunderbird to version 140.11 or later
  • Monitor Mozilla security advisories for additional guidance
  • Review application whitelisting policies for Mozilla products in enterprise environments

Evidence notes

The vulnerability description and affected versions are derived from official Mozilla security advisories and NVD records. The CVSS vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N) indicates network attack vector with low attack complexity, no privileges required, no user interaction, and impacts to confidentiality and integrity but not availability.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-8388 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-8388

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-8388 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-8388

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.