CVE-2018-20989 in untrusted Crate
Summary
by MITRE
An issue was discovered in the untrusted crate before 0.6.2 for Rust. Error handling can trigger an integer underflow and panic.
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Analysis
by VulDB Data Team • 12/04/2023
The vulnerability identified as CVE-2018-20989 affects the Rust programming language ecosystem through a problematic crate that failed to properly handle error conditions. This issue specifically manifests in versions prior to 062 and represents a critical flaw in the error handling mechanisms of the affected library. The vulnerability exists within the crate's implementation where improper validation of integer values during error processing can lead to unexpected behavior. When error conditions are encountered, the system attempts to perform arithmetic operations on integer values that can fall below their minimum representable bounds, resulting in an integer underflow condition.
The technical exploitation of this vulnerability occurs when the crate processes error scenarios that involve integer calculations. During normal operation, when errors are encountered, the system may attempt to adjust integer values to determine error codes or handle resource management. However, due to inadequate bounds checking, these operations can cause integers to wrap around to extremely negative values, triggering a panic condition that terminates the application. This type of vulnerability falls under the category of integer underflow as classified by CWE-191, which specifically addresses issues where integer underflow occurs during arithmetic operations. The panic state created by this underflow can be exploited to cause denial of service conditions, potentially allowing attackers to crash applications that depend on this crate.
The operational impact of CVE-2018-20989 extends beyond simple application crashes, as it can affect the reliability and stability of systems that utilize affected Rust crates. When applications encounter error conditions, they may unexpectedly terminate, leading to service disruption and potential data loss. This vulnerability is particularly concerning in production environments where Rust applications may be processing critical workloads or serving multiple users simultaneously. The panic condition can propagate through application stacks, potentially affecting entire service availability. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, as successful exploitation can cause applications to become unresponsive or crash entirely. The vulnerability also represents a weakness in the software supply chain, as it affects dependencies that many Rust applications rely upon for proper error handling functionality.
Mitigation strategies for CVE-2018-20989 primarily involve updating to version 062 or later of the affected crate, which contains proper integer bounds checking and error handling mechanisms. System administrators and developers should conduct thorough dependency audits to identify all applications using the vulnerable crate and ensure timely updates are deployed across their environments. Additionally, implementing proper input validation and error handling practices within application code can provide additional defense in depth. Organizations should also consider implementing monitoring solutions that can detect unexpected application panics or crashes, as these events may indicate exploitation attempts. The fix implemented in version 062 addresses the root cause by ensuring that integer values are properly validated before arithmetic operations are performed, preventing the underflow conditions that previously led to panic states. Security teams should also consider implementing automated vulnerability scanning tools that can identify outdated dependencies and alert on potential exposure to similar integer overflow vulnerabilities in their Rust-based applications.