CVE-2017-9103 in adns
Summary
by MITRE
An issue was discovered in adns before 1.5.2. pap_mailbox822 does not properly check st from adns__findlabel_next. Without this, an uninitialised stack value can be used as the first label length. Depending on the circumstances, an attacker might be able to trick adns into crashing the calling program, leaking aspects of the contents of some of its memory, causing it to allocate lots of memory, or perhaps overrunning a buffer. This is only possible with applications which make non-raw queries for SOA or RP records.
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Analysis
by VulDB Data Team • 05/15/2023
The vulnerability described in CVE-2017-9103 affects the adns library version 1.5.1 and earlier, representing a critical security flaw in DNS resolution handling that can lead to multiple exploitation vectors. This issue resides in the pap_mailbox822 function which fails to properly validate the st parameter obtained from adns__findlabel_next, creating a dangerous condition where uninitialized stack values can be utilized as the first label length in DNS record processing. The root cause of this vulnerability stems from inadequate input validation and memory management practices within the DNS parsing routines, specifically when handling certain record types such as SOA and RP records.
The technical implementation of this vulnerability exploits a classic uninitialized variable flaw that falls under CWE-457, where a program attempts to use a variable that has not been initialized. When applications make non-raw queries for SOA or RP DNS records, the malformed processing can cause the adns library to utilize stack memory that contains arbitrary data as a length indicator for DNS labels. This uninitialized stack value can be interpreted as a legitimate label length, potentially leading to several dangerous outcomes including denial of service through program crashes, memory disclosure attacks that leak sensitive information from the program's memory space, excessive memory allocation patterns that can exhaust system resources, or even buffer overflow conditions that could be exploited for arbitrary code execution. The vulnerability specifically targets the interaction between the DNS resolution library and applications that perform standard DNS queries rather than raw socket operations.
The operational impact of CVE-2017-9103 extends beyond simple service disruption to encompass potential information disclosure and system stability threats. Attackers leveraging this vulnerability can cause applications using the affected adns library to behave unpredictably, potentially leading to complete application crashes or memory corruption that might expose sensitive data from the program's memory segments. The exploitation requires specific conditions where applications perform non-raw DNS queries for SOA or RP records, making it particularly relevant to mail servers, DNS resolvers, and any system that relies on standard DNS resolution for network communications. This vulnerability aligns with ATT&CK technique T1059.007 for DNS tunneling and command execution, though the primary impact is through denial of service and information disclosure rather than direct execution. The memory disclosure aspect of this vulnerability particularly concerns security practitioners as it could expose cryptographic keys, session tokens, or other sensitive information stored in the program's memory space. The vulnerability demonstrates how seemingly minor input validation issues in core networking libraries can create cascading security problems for entire application ecosystems. Organizations using affected versions of adns should immediately implement patch updates to version 1.5.2 or later, and security teams should monitor for potential exploitation attempts targeting this specific DNS parsing flaw. The vulnerability also highlights the importance of proper memory initialization practices in network protocol implementations and the need for comprehensive testing of DNS resolution libraries under various input conditions.