CVE-2026-5731 | Mozilla Firefox up to 149.0.1 memory corruption

VDB-355739 · CVE-2026-5731 · GCVE-0-2026-5731 MOZILLA FIREFOX UP TO 149.0.1 MEMORY CORRUPTION HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 6.0 $5k-$25k 1.22+ Summaryinfo A vulnerability classified as critical has been found in Mozilla Firefox up to 149.0.1. Affected is an unknown function. The manipulation leads to memory corruption. This vulnerability is traded as CVE-2026-5731. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component. Detailsinfo A vulnerability was found in Mozilla Firefox up to 149.0.1 and classified as critical. This issue affects some unknown processing. The manipulation with an unknown input leads to a memory corruption vulnerability. Using CWE to declare the problem leads to CWE-119. The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer. Impacted is confidentiality, integrity, and availability. The summary by CVE is: Memory safety bugs present in Firefox ESR 115.34.0, Firefox ESR 140.9.0, Thunderbird ESR 140.9.0, Firefox 149.0.1 and Thunderbird 149.0.1. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 149.0.2, Firefox ESR < 115.34.1, and Firefox ESR < 140.9.1. The identification of this vulnerability is CVE-2026-5731 since 04/07/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 04/07/2026). Upgrading to version 149.0.2 eliminates this vulnerability. Productinfo Type Web Browser Vendor Mozilla Name Firefox Version 149.0.0 149.0.1 License open-source Website Vendor: https://www.mozilla.org/ Product: https://www.mozilla.org/en-US/firefox/ CPE 2.3info 🔒 🔒 CPE 2.2info 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 6.3 VulDB Meta Temp Score: 6.0 VulDB Base Score: 6.3 VulDB Temp Score: 6.0 VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Memory corruption CWE: CWE-119 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: Firefox 149.0.2 Timelineinfo 04/07/2026 Advisory disclosed 04/07/2026 +0 days CVE reserved 04/07/2026 +0 days VulDB entry created 04/07/2026 +0 days VulDB entry last update Sourcesinfo Vendor: mozilla.org Product: mozilla.org Status: Confirmed CVE: CVE-2026-5731 (🔒) GCVE (CVE): GCVE-0-2026-5731 GCVE (VulDB): GCVE-100-355739 Entryinfo Created: 04/07/2026 15:28 Changes: 04/07/2026 15:28 (54) Complete: 🔍 Cache ID: 99:FEF:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸