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Mozilla NSS CVE-2026-16389

| EUVDEUVD-2026-46226 CRITICAL
Integer Overflow or Wraparound (CWE-190)
2026-07-21 mozilla GHSA-52h6-3xqw-4r8v
Buffer Overflow Integer Overflow Mozilla
Critical
Disputed · 9.8 Vendor: mozilla
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Severity by source

Sources disagree (Medium–Critical)
Vendor (mozilla) PRIMARY
9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
7.5 HIGH

Network-reachable NSS parsing (AV:N) but requires victim to connect to attacker content (UI:R) and reliable overflow control is nontrivial (AC:H); memory corruption yields full C/I/A impact.

3.1 AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
4.0 AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SUSE
CRITICAL
qualitative
Red Hat
6.1 MEDIUM
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: mozilla

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Analysis Generated
Jul 22, 2026 - 19:03 vuln.today
CVSS changed
Jul 22, 2026 - 18:22 NVD
9.8 (CRITICAL)
CVE Published
Jul 21, 2026 - 12:38 cve.org
UNKNOWN (no severity yet)
CVE Published
Jul 21, 2026 - 12:38 cve.org
CRITICAL 9.8

DescriptionCVE.org

Incorrect boundary conditions, integer overflow in the Libraries component in NSS. This vulnerability was fixed in Firefox 153.

AnalysisAI

Memory-safety compromise in Mozilla's NSS (Network Security Services) cryptographic library allows remote attackers to trigger an integer overflow that leads to out-of-bounds memory access, remediated in Firefox 153 (advisory MFSA2026-68). The flaw stems from incorrect boundary conditions during size calculations in NSS Libraries code, and because NSS handles TLS/certificate and cryptographic parsing, malicious network-supplied data can reach the vulnerable path without user authentication. No public exploit identified at time of analysis, and EPSS is low (0.14%, 4th percentile), indicating no observed weaponization despite the critical CVSS score.

Technical ContextAI

NSS (Network Security Services) is Mozilla's foundational cryptographic library providing TLS/SSL, PKCS, S/MIME, and X.509 certificate handling for Firefox and numerous other products. The root cause is CWE-190 (Integer Overflow or Wraparound): a size or length computation in an NSS Libraries component wraps around its integer type due to incorrect boundary checks, producing an undersized allocation or a miscalculated index that subsequently drives an out-of-bounds read or write (consistent with the 'Buffer Overflow' tag). Because NSS parses attacker-influenced binary structures (certificates, cryptographic messages, TLS handshake data), overflow conditions in these length calculations are directly reachable from remote input. The affected CPE is cpe:2.3:a:mozilla:firefox (all versions prior to 153), with NSS being the shared library where the defect lives.

RemediationAI

Vendor-released patch: upgrade to Firefox 153 or later, which contains the corrected NSS boundary/size checks per Mozilla advisory MFSA2026-68 (https://www.mozilla.org/security/advisories/mfsa2026-68/). This is the primary and recommended remediation and requires no configuration changes. For environments that also embed NSS independently (Thunderbird, other TLS clients linking NSS), update to the NSS release that Mozilla shipped alongside Firefox 153 and rebuild/redeploy affected applications. No supported standalone workaround fully mitigates a library-level integer overflow, but as an interim compensating control you can reduce exposure by restricting Firefox's processing of untrusted content - enforce browsing through a filtering proxy, limit TLS connections to known/allow-listed endpoints, and deploy at network egress; note these controls degrade usability and do not address non-web NSS consumers. Track and apply the fix promptly given the critical CVSS rating even though EPSS indicates low current exploitation likelihood.

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Same weakness CWE-190 – Integer Overflow or Wraparound

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CVE-2013-2729 CRITICAL POC
9.8
CVE-2015-8651 HIGH
8.8
CVE-2012-5054 HIGH POC
8.8
CVE-2014-0569 CRITICAL POC
9.3
CVE-2023-21716 CRITICAL POC
9.8
CVE-2017-3599 HIGH POC
7.5
CVE-2017-7529 HIGH
7.5
CVE-2016-1010 HIGH
8.8

Same technique Buffer Overflow

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CVE-2017-7269 CRITICAL POC
9.8
CVE-2015-5119 CRITICAL POC
9.8
CVE-2015-3113 CRITICAL POC
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CVE-2011-2462 CRITICAL POC
9.8
CVE-2020-0796 CRITICAL POC
10.0
CVE-2019-11043 CRITICAL POC
9.8
CVE-2009-0927 HIGH POC
8.8
CVE-2012-1889 HIGH POC
8.8

Vendor StatusVendor

SUSE

Severity: Critical
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Module for Desktop Applications 15 SP7 Affected
SUSE Linux Enterprise Module for Package Hub 15 SP7 Affected

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CVE-2026-16389 vulnerability details – vuln.today
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