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CVE-2026-4371— Out of bounds read in IMAP parsing

Quick assessment

Affected
Mozilla Thunderbird
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mozilla Thunderbird是美国Mozilla基金会的一套从Mozilla Application Suite独立出来的电子邮件客户端软件。该软件支持IMAP、POP邮件协议以及HTML邮件格式。 Mozilla Thunderbird 149之前版本和140.9之前版本存在安全漏洞，该漏洞源于解析器可能读取缓冲区外的内存，可能导致崩溃或敏感数据泄露。

AI Predicted 4.3 Difficulty: Hard EPSS 0.64% · P49

Affected Version Matrix 2

VendorProduct Version RangeStatus
Mozilla Thunderbird 140.9≤ 140.* unaffected
149≤ * unaffected
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I. Basic Information for CVE-2026-4371

Vulnerability Information
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Vulnerability Title
Out of bounds read in IMAP parsing
Source: CVE Program / CVE List V5
Vulnerability Description
A malicious mail server could send malformed strings with negative lengths, causing the parser to read memory outside the buffer. If a mail server or connection to a mail server were compromised, an attacker could cause the parser to malfunction, potentially crashing Thunderbird or leaking sensitive data. This vulnerability was fixed in Thunderbird 149 and Thunderbird 140.9.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Mozilla Thunderbird 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mozilla Thunderbird是美国Mozilla基金会的一套从Mozilla Application Suite独立出来的电子邮件客户端软件。该软件支持IMAP、POP邮件协议以及HTML邮件格式。 Mozilla Thunderbird 149之前版本和140.9之前版本存在安全漏洞，该漏洞源于解析器可能读取缓冲区外的内存，可能导致崩溃或敏感数据泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mozilla Thunderbird 140.9 ~ 140.* -

II. Public POCs for CVE-2026-4371

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III. Intelligence Information for CVE-2026-4371

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Vendor Advisories for CVE-2026-4371 (2)

Same Patch Batch · Mozilla · 2026-03-24 · 47 CVEs total

CVE-2026-4714 Incorrect boundary conditions in the Audio/Video component
CVE-2026-4717 Privilege escalation in the Netmonitor component
CVE-2026-4726 Denial-of-service in the XML component
CVE-2026-4720 Memory safety bugs fixed in Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thun
CVE-2026-4719 Incorrect boundary conditions in the Graphics: Text component
CVE-2026-4729 Memory safety bugs fixed in Firefox 149 and Thunderbird 149
CVE-2026-4721 Memory safety bugs fixed in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9,
CVE-2026-3889 Spoofing issue in Thunderbird
CVE-2026-4718 Undefined behavior in the WebRTC: Signaling component
CVE-2026-4715 Uninitialized memory in the Graphics: Canvas2D component
CVE-2026-4716 Incorrect boundary conditions, uninitialized memory in the JavaScript Engine component
CVE-2026-4713 Incorrect boundary conditions in the Graphics component
CVE-2026-4725 Sandbox escape due to use-after-free in the Graphics: Canvas2D component
CVE-2026-4712 Information disclosure in the Widget: Cocoa component
CVE-2026-4710 Incorrect boundary conditions in the Audio/Video component
CVE-2026-4711 Use-after-free in the Widget: Cocoa component
CVE-2026-4709 Incorrect boundary conditions in the Audio/Video: GMP component
CVE-2026-4708 Incorrect boundary conditions in the Graphics component
CVE-2026-4707 Incorrect boundary conditions in the Graphics: Canvas2D component
CVE-2026-4706 Incorrect boundary conditions in the Graphics: Canvas2D component

Showing top 20 of 47 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: Thunderbird
Same vendor: Mozilla

V. Comments for CVE-2026-4371

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