CVE-2017-9106 in adns
Summary
by MITRE
An issue was discovered in adns before 1.5.2. adns_rr_info mishandles a bogus *datap. The general pattern for formatting integers is to sprintf into a fixed-size buffer. This is correct if the input is in the right range; if it isn't, the buffer may be overrun (depending on the sizes of the types on the current platform). Of course the inputs ought to be right. And there are pointers in there too, so perhaps one could say that the caller ought to check these things. It may be better to require the caller to make the pointer structure right, but to have the code here be defensive about (and tolerate with an error but without crashing) out-of-range integer values. So: it should defend each of these integer conversion sites with a check for the actual permitted range, and return adns_s_invaliddata if not. The lack of this check causes the SOA sign extension bug to be a serious security problem: the sign extended SOA value is out of range, and overruns the buffer when reconverted. This is related to sign extending SOA 32-bit integer fields, and use of a signed data type.
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Analysis
by VulDB Data Team • 05/15/2023
The vulnerability described in CVE-2017-9106 represents a critical buffer overflow issue within the adns library version 1.5.1 and earlier. This flaw manifests in the adns_rr_info function which improperly handles malformed data pointers, creating a scenario where integer formatting operations can lead to memory corruption. The core issue stems from the library's reliance on fixed-size buffers for integer conversion operations through sprintf functions, a pattern that becomes dangerous when input values exceed expected ranges. The vulnerability specifically impacts the handling of SOA (Start of Authority) resource records where 32-bit integer fields undergo sign extension operations that result in values outside the permissible range for buffer allocation.
The technical implementation of this vulnerability exposes a fundamental design flaw in input validation and error handling within the DNS resolution library. When processing SOA records, the code performs sign extension on 32-bit integer fields without proper range checking, leading to values that exceed the bounds of the fixed-size buffers used for string formatting. This creates a classic buffer overflow condition where the sprintf function attempts to write beyond the allocated memory space, potentially corrupting adjacent memory regions. The problem is exacerbated by the fact that the calling code does not adequately validate the pointer structures or input data ranges before passing them to adns_rr_info, leaving the library vulnerable to maliciously crafted DNS responses that exploit this weakness.
The operational impact of CVE-2017-9106 extends beyond simple memory corruption to potentially enable arbitrary code execution within applications that utilize the affected adns library. This vulnerability falls under CWE-121, which describes stack-based buffer overflow conditions, and is particularly dangerous because it can be triggered through DNS resolution operations that are fundamental to network communication. Attackers can craft malicious DNS SOA records that, when processed by vulnerable applications, cause the buffer overflow to occur during the conversion of sign-extended values back to strings. The vulnerability's severity is amplified by its potential for remote exploitation, as DNS resolution is a common operation in networked applications, making this a significant concern for systems that depend on DNS lookups for various services including web browsing, email processing, and network authentication.
Mitigation strategies for this vulnerability require implementing defensive programming practices that align with the principle of least privilege and input validation. The recommended approach involves adding explicit range checks for integer conversion operations within the adns_rr_info function, specifically targeting the sign extension handling of SOA fields. This defensive mechanism should validate integer values against their expected ranges before processing and return appropriate error codes such as adns_s_invaliddata when out-of-range values are detected. The fix should also incorporate bounds checking for all pointer operations and buffer operations, ensuring that the library gracefully handles malformed input rather than crashing or corrupting memory. Additionally, system administrators should prioritize updating to adns version 1.5.2 or later where this vulnerability has been addressed through proper input validation and error handling mechanisms that prevent the buffer overflow condition from occurring. This vulnerability demonstrates the importance of following ATT&CK technique T1059.007 for input validation and T1059.008 for privilege escalation prevention, as proper validation would prevent the exploitation pathway that leads to memory corruption and potential code execution.