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    CVE-2020-7957

    The IMAP and LMTP components in Dovecot 2.3.9 before 2.3.9.3 mishandle snippet generation when many characters must be read to compute the snippet and a trailing > character exists. This causes a denial of service in which the recipient cannot read all of their messages.

    Published:Feb 12, 2020
    Last Modified:Nov 21, 2024
    EPS:Feb 12, 2020
    EPSS Score:0.00366
    CVSS Score:5.3

    Affected Products

    Vendor
    Dovecot
    Product
    Dovecot
    Vendor
    Fedoraproject
    Product
    Fedora

    Exploits

    http://www.openwall.com/lists/oss-security/2020/02/12/2https://dovecot.org/pipermail/dovecot-news/2020-February/000430.htmlhttp://www.openwall.com/lists/oss-security/2020/02/12/2https://dovecot.org/pipermail/dovecot-news/2020-February/000430.html

    Common Weakness Enumeration

    CWE-20 Improper Input Validation

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-10 Buffer Overflow via Environment Variables
    CAPEC-101 Server Side Include (SSI) Injection
    CAPEC-104 Cross Zone Scripting
    CAPEC-108 Command Line Execution through SQL Injection
    CAPEC-109 Object Relational Mapping Injection
    CAPEC-110 SQL Injection through SOAP Parameter Tampering
    CAPEC-120 Double Encoding
    CAPEC-13 Subverting Environment Variable Values
    CAPEC-135 Format String Injection
    CAPEC-136 LDAP Injection
    CAPEC-14 Client-side Injection-induced Buffer Overflow
    CAPEC-153 Input Data Manipulation
    CAPEC-182 Flash Injection
    CAPEC-209 XSS Using MIME Type Mismatch
    CAPEC-22 Exploiting Trust in Client
    CAPEC-23 File Content Injection
    CAPEC-230 Serialized Data with Nested Payloads
    CAPEC-231 Oversized Serialized Data Payloads
    CAPEC-24 Filter Failure through Buffer Overflow
    CAPEC-250 XML Injection
    CAPEC-261 Fuzzing for garnering other adjacent user/sensitive data
    CAPEC-267 Leverage Alternate Encoding
    CAPEC-28 Fuzzing
    CAPEC-3 Using Leading 'Ghost' Character Sequences to Bypass Input Filters
    CAPEC-31 Accessing/Intercepting/Modifying HTTP Cookies
    CAPEC-42 MIME Conversion
    CAPEC-43 Exploiting Multiple Input Interpretation Layers
    CAPEC-45 Buffer Overflow via Symbolic Links
    CAPEC-46 Overflow Variables and Tags
    CAPEC-47 Buffer Overflow via Parameter Expansion
    CAPEC-473 Signature Spoof
    CAPEC-52 Embedding NULL Bytes
    CAPEC-53 Postfix, Null Terminate, and Backslash
    CAPEC-588 DOM-Based XSS
    CAPEC-63 Cross-Site Scripting (XSS)
    CAPEC-64 Using Slashes and URL Encoding Combined to Bypass Validation Logic
    CAPEC-664 Server Side Request Forgery
    CAPEC-67 String Format Overflow in syslog()
    CAPEC-7 Blind SQL Injection
    CAPEC-71 Using Unicode Encoding to Bypass Validation Logic
    CAPEC-72 URL Encoding
    CAPEC-73 User-Controlled Filename
    CAPEC-78 Using Escaped Slashes in Alternate Encoding
    CAPEC-79 Using Slashes in Alternate Encoding
    CAPEC-8 Buffer Overflow in an API Call
    CAPEC-80 Using UTF-8 Encoding to Bypass Validation Logic
    CAPEC-81 Web Server Logs Tampering
    CAPEC-83 XPath Injection
    CAPEC-85 AJAX Footprinting
    CAPEC-88 OS Command Injection
    CAPEC-9 Buffer Overflow in Local Command-Line Utilities

    Related CVEs

    CVE-2026-42006 (CVSS 4.3) — An attacker can cause uncontrolled memory usage with excessive bracing over IMAP. The fix in CVE-2026-27857 wa…
    CVE-2026-40020 (CVSS 3.1) — Attacker can use the IMAP SETACL command to inject the anyone permission to user's dovecot-acl file even if im…
    CVE-2026-40016 (CVSS 5.3) — Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU ti…
    CVE-2026-33603 (CVSS 6.8) — Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel bind…
    CVE-2026-27851 (CVSS 7.4) — When safe filter is used with variable expansion, all following pipelines on the same string are incorrectly i…
    CVE-2026-27860 (CVSS 3.7) — If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authenticati…
    CVE-2026-27859 (CVSS 5.3) — A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU. A suit…
    CVE-2026-27858 (CVSS 7.5) — Attacker can send a specifically crafted message before authentication that causes managesieve to allocate lar…
    CVE-2026-27857 (CVSS 4.3) — Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer c…
    CVE-2026-27856 (CVSS 7.4) — Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An atta…

    References

    http://www.openwall.com/lists/oss-security/2020/02/12/2
    https://dovecot.org/pipermail/dovecot-news/2020-February/000430.html
    https://dovecot.org/security
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6XYT55WH372BJOXCJRKBDIFGBMPVOIDT/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NJXHOUT3FH2DJNMACSX4GHPP4MUV4UKA/
    http://www.openwall.com/lists/oss-security/2020/02/12/2
    https://dovecot.org/pipermail/dovecot-news/2020-February/000430.html
    https://dovecot.org/security
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6XYT55WH372BJOXCJRKBDIFGBMPVOIDT/
    https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NJXHOUT3FH2DJNMACSX4GHPP4MUV4UKA/

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High