CVE-2026-96674 in alsa-lib
Summary
by MITRE • 09/23/2026
alsa-lib through 1.2.16.1 computes combined topology element size using 32-bit arithmetic in src/topology/ctl.c, allowing integer overflow that defeats bounds checks. Attackers can supply crafted topology files that wrap size calculations, causing the decoder to read beyond the topology buffer and potentially leak sensitive data or crash the application.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability identified in alsa-lib versions through 1.2.16.1 represents a critical integer overflow flaw located within the sound card configuration parsing logic, specifically in the source file src/topology/ctl.c. This component is responsible for decoding topology elements that define how audio hardware interfaces with software drivers. The core technical defect arises from the method used to compute the combined size of these topology elements. Instead utilizing data types capable of handling larger values or implementing explicit overflow checks before arithmetic operations, the library relies on standard 32-bit integer arithmetic. This design choice creates a scenario where sufficiently large input values can wrap around due to modulo arithmetic inherent in fixed-width integers. When an attacker supplies a crafted topology file containing specific size parameters that exceed the maximum value representable by a signed or unsigned thirty-two bit integer, the addition operation results in a significantly smaller positive number than intended. This wrapped value is then used as a bound for subsequent memory operations, effectively bypassing safety checks designed to prevent buffer overflows.
The operational impact of this flaw is severe because it allows an attacker who can influence the topology configuration loaded by alsa-lib to trigger out-of-bounds reads from system memory. Since the decoder believes the required buffer size is small due to the integer wrap-around, it proceeds to read data beyond the allocated boundaries of the topology buffer. This behavior constitutes a classic information disclosure vulnerability where sensitive data residing in adjacent memory locations can be leaked back to the user space application or potentially used for further exploitation steps such as heap spraying or address leakage. In scenarios where robust error handling is not implemented around these reads, the process may also encounter segmentation faults or other undefined behaviors leading to denial of service conditions that crash the audio subsystem or any dependent applications relying on alsa-lib for sound processing.
From a classification perspective, this vulnerability aligns with CWE-190 Integer Overflow or Wraparound, which describes situations where arithmetic operations exceed the capacity of the data type used, resulting in unexpected values. The exploitation technique leverages this flaw to bypass bounds checks, mapping directly to CWE-787 Out-of-bounds Read within the Common Weakness Enumeration framework. In terms of offensive security tactics, this vulnerability facilitates reconnaissance and credential access phases by allowing an attacker to extract sensitive memory contents without requiring elevated privileges initially if they can inject or manipulate configuration files accessible to the audio service. This maps to ATT&CK techniques related to Data from Local System such as Memory Dumping or potentially Command and Control if used in conjunction with other vulnerabilities for remote code execution chains, although primarily it serves as an information leak vector here.
Mitigation strategies must focus on both immediate patching and long-term defensive coding practices. The primary remediation is to upgrade alsa-lib to version 1.2.16.2 or later where this integer overflow has been addressed by implementing proper size validation before arithmetic operations occur. Developers should enforce the use of larger data types such as sixty-four-bit integers for size calculations involving user-supplied inputs to prevent wrap-around scenarios. Additionally, input validation routines must be strengthened to ensure that computed sizes do not exceed predefined maximum limits or allocated buffer capacities before any memory access is attempted. Security audits should prioritize reviewing all arithmetic operations in parsing logic for similar overflow risks, ensuring that bounds checks are performed using values that cannot be manipulated through integer wrapping techniques.