CVE-2026-90781 in alsa-lib
Summary
by MITRE • 09/13/2026
alsa-lib through 1.2.16.1 contains a stack buffer overflow in the __snd_ctl_ascii_elem_id_parse() function that writes one byte past a 64-byte buffer when parsing a name= field with 64 or more characters. Attackers can supply a long control-element identifier string through saved state files or command-line arguments to overwrite adjacent stack memory and crash the calling process.
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Analysis
by VulDB Data Team • 09/13/2026
The vulnerability identified in alsa-lib versions up to 1.2.16.1 represents a critical stack-based buffer overflow within the audio subsystem, specifically located in the __snd_ctl_ascii_elem_id_parse() function. This component is responsible for parsing control element identifiers from ASCII strings, which are commonly encountered when applications interact with ALSA sound cards via configuration files or command-line inputs. The core technical flaw stems from an insufficient bounds check during string processing operations. When the parser encounters a name field containing sixty-four characters or more, it fails to account for the null terminator and potentially other internal state variables stored on the stack immediately following the buffer allocation. Consequently, the write operation extends one byte beyond the allocated sixteenth-byte boundary, corrupting adjacent memory locations that hold critical execution context data such as return addresses or saved frame pointers.
This specific overflow mechanism classifies under CWE-121, which denotes a stack-based buffer overflow where input validation is inadequate to prevent writing past the end of a fixed-size array on the call stack. The vulnerability is particularly insidious because it does not require complex exploitation techniques for initial impact; rather, it relies on straightforward memory corruption that can be triggered by relatively simple inputs. An attacker who controls the content of saved state files or command-line arguments passed to an application utilizing alsa-lib can inject a maliciously crafted string designed to overwrite these adjacent stack variables. While overwriting only one byte may seem limited in scope, its position relative to control data on the stack is often decisive for achieving arbitrary code execution or causing immediate denial of service conditions depending on the specific compiler optimizations and architecture involved.
The operational impact of this vulnerability centers primarily on availability and potentially integrity if exploitation leads to controlled memory corruption. In most practical scenarios, triggering this overflow results in a segmentation fault that crashes the calling process immediately. For desktop environments where audio services run as persistent background daemons or for applications like media players and communication tools that frequently parse user-provided configuration data, such crashes can lead to significant service disruption. If an attacker can force repeated crashes of critical system components, they may achieve a denial-of-service condition against the host machine. Furthermore, in environments where alsa-lib is embedded within privileged processes or setuid binaries, this memory corruption could potentially be leveraged for privilege escalation by manipulating return addresses or function pointers to redirect execution flow to malicious shellcode placed elsewhere in memory.
From an offensive security perspective, this vulnerability aligns with ATT&CK technique T1059, specifically sub-techniques related to command and script interpreters if triggered via CLI arguments, or T1204 for user execution if leveraged through crafted state files that trick a user into launching a vulnerable application. The attack vector is considered local unless the alsa-lib interface is exposed over a network service in an unusual configuration, making remote exploitation unlikely without additional vectors such as web applications that process audio configurations uploaded by users. Defense-in-depth strategies should be employed to mitigate this risk since patching alone may not always be immediately available for all dependent systems.
Mitigation efforts must prioritize updating alsa-lib to version 1.2.16.1 or later, where the parsing logic has been corrected to enforce strict length limits and properly handle null terminators within the __snd_ctl_ascii_elem_id_parse() function. For organizations unable to patch immediately due to dependency constraints, implementing input validation at higher-level application layers can serve as a temporary compensating control by sanitizing any user-supplied strings before they are passed to ALSA functions. Additionally, enabling compiler security features such as stack protectors and Address Space Layout Randomization reduces the likelihood of successful exploitation even if the overflow occurs, as these mechanisms make it significantly harder for attackers to predict memory layouts or overwrite return addresses reliably. Regular auditing of third-party library usage within audio processing pipelines is also recommended to ensure that no legacy code paths remain vulnerable to similar parsing errors in other components.