CVE-2026-121943
Description
A flaw was found in sngrep. An out-of-bounds stack read vulnerability exists due to an off-by-one length check when parsing Session Initiation Protocol (SIP) payloads. A remote attacker could exploit this by sending a crafted network packet or supplying a malicious packet capture file, resulting in a Denial of Service (DoS) via an application crash or information disclosure of stack memory.
Statement
This vulnerability is rated as Moderate severity because exploitation requires an active capture session or manual processing of an untrusted capture file, limiting the blast radius to the diagnostic process without compromising underlying system integrity. Additionally, sngrep is an interactive command-line diagnostic tool rather than a continuously running system service, significantly reducing exposure on production environments. Red Hat does not package or distribute sngrep, and the issue primarily impacts community distributions such as Fedora when the tool is manually invoked.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability
Technical Impact: Read Memory; Execute Unauthorized Code or Commands
The case of an omitted null character is the most dangerous of the possible issues. This will almost certainly result in information disclosure, and possibly a buffer overflow condition, which may be exploited to execute arbitrary code.
Confidentiality,Integrity,Availability
Technical Impact: DoS: Crash, Exit, or Restart; Read Memory; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory)
If a null character is omitted from a string, then most string-copying functions will read data until they locate a null character, even outside of the intended boundaries of the string. This could: cause a crash due to a segmentation fault cause sensitive adjacent memory to be copied and sent to an outsider trigger a buffer overflow when the copy is being written to a fixed-size buffer.
Integrity,Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart
Misplaced null characters may result in any number of security problems. The biggest issue is a subset of buffer overflow, and write-what-where conditions, where data corruption occurs from the writing of a null character over valid data, or even instructions. A randomly placed null character may put the system into an undefined state, and therefore make it prone to crashing. A misplaced null character may corrupt other data in memory.
Integrity,Confidentiality,Availability,Access Control,Other
Technical Impact: Alter Execution Logic; Execute Unauthorized Code or Commands
Should the null character corrupt the process flow, or affect a flag controlling access, it may lead to logical errors which allow for the execution of arbitrary code.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
