CVE-2022-1620 in vim
Summary
by MITRE • 05/08/2022
NULL Pointer Dereference in function vim_regexec_string at regexp.c:2729 in GitHub repository vim/vim prior to 8.2.4901. NULL Pointer Dereference in function vim_regexec_string at regexp.c:2729 allows attackers to cause a denial of service (application crash) via a crafted input.
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Analysis
by VulDB Data Team • 04/07/2026
The vulnerability identified as CVE-2022-1620 represents a critical null pointer dereference flaw within the vim text editor's regular expression engine. This issue exists in the vim_regexec_string function located at line 2729 in the regexp.c source file of the vim repository. The vulnerability affects versions prior to 8.2.4901 and demonstrates how improper input validation can lead to application instability. The flaw occurs when the regular expression engine processes malformed input patterns, causing the software to attempt to dereference a null pointer during pattern matching operations. This type of vulnerability falls under the category of CWE-476 which specifically addresses null pointer dereference conditions that can result in application crashes or potential exploitation. The vulnerability is particularly concerning because it can be triggered through crafted input, making it susceptible to denial of service attacks where an attacker can deliberately cause the application to crash by providing malicious regular expression patterns.
The technical implementation of this vulnerability stems from inadequate error handling within the regular expression execution logic. When vim processes regular expression patterns, it maintains internal data structures that track pattern matching states and memory references. During the execution of vim_regexec_string, the software fails to properly validate pointer references before dereferencing them, specifically when handling certain edge cases in pattern matching. The null pointer dereference occurs at a critical execution point where the software assumes certain memory locations contain valid data but encounters null references instead. This behavior aligns with ATT&CK technique T1499.004 which describes denial of service attacks through application crashes or resource exhaustion. The vulnerability's exploitation path involves feeding the vim editor with specially crafted regular expression patterns that trigger the specific code path leading to the null pointer dereference, resulting in an immediate application crash without any possibility of recovery.
The operational impact of CVE-2022-1620 extends beyond simple application instability to potentially disrupt user workflows and system availability in environments where vim is extensively used. In server environments or automated systems that rely on vim for text processing, this vulnerability could be exploited to cause service disruption through repeated denial of service attacks. The vulnerability affects both local and remote attack scenarios since vim can be invoked through various interfaces including command line operations, scripts, or web-based applications that utilize vim functionality. Security implications include potential escalation to more severe attacks if the vulnerability exists in environments where vim is used with elevated privileges or in critical system components. Organizations using vim in production environments must consider the risk of this vulnerability being exploited in automated attack scenarios, particularly in systems where vim is integrated with other applications or used in security-critical workflows.
Mitigation strategies for CVE-2022-1620 primarily focus on immediate version updates to address the root cause of the vulnerability. Users should upgrade to vim version 8.2.4901 or later where the null pointer dereference issue has been resolved through proper input validation and pointer checking mechanisms. System administrators should implement patch management procedures to ensure all vim installations are updated promptly, particularly in environments where the editor is used with untrusted input. Additional protective measures include implementing input sanitization for regular expression patterns when processing user-provided data, and configuring access controls to limit the exposure of vim to potentially malicious inputs. Network security controls such as intrusion detection systems can be configured to monitor for patterns that might indicate exploitation attempts targeting this vulnerability. Organizations should also consider implementing application whitelisting policies that restrict the execution of vim with untrusted input sources and establish monitoring procedures to detect application crashes or abnormal behavior that might indicate exploitation attempts. The fix implemented in the patched version addresses the core issue by adding proper null pointer checks before dereferencing memory locations and ensures that regular expression execution gracefully handles malformed input patterns without causing application termination.