CVE-2026-28421 in vim
Summary
by MITRE • 02/28/2026
Vim is an open source, command line text editor. Versions prior to 9.2.0077 have a heap-buffer-overflow and a segmentation fault (SEGV) exist in Vim's swap file recovery logic. Both are caused by unvalidated fields read from crafted pointer blocks within a swap file. Version 9.2.0077 fixes the issue.
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Analysis
by VulDB Data Team • 04/16/2026
The vulnerability identified as CVE-2026-28421 affects Vim text editor versions prior to 9.2.0077, presenting critical security risks through heap buffer overflow and segmentation fault conditions during swap file recovery operations. This issue stems from insufficient validation of fields within crafted pointer blocks contained in swap files, creating exploitable conditions that can compromise system integrity. The vulnerability specifically targets Vim's recovery logic when processing swap files that have been manipulated to contain maliciously crafted data structures, particularly pointer blocks that are not properly validated before use.
The technical flaw manifests in Vim's handling of swap file recovery mechanisms where the software reads pointer block information without adequate validation checks. When a swap file contains crafted pointer blocks with malformed or oversized field values, the recovery process attempts to allocate memory or access memory regions based on these unvalidated inputs. This leads to heap buffer overflow conditions where data is written beyond allocated memory boundaries, potentially allowing attackers to overwrite adjacent memory locations or cause memory corruption that can be exploited for arbitrary code execution. Additionally, the segmentation fault occurs when the software attempts to access invalid memory addresses or performs operations on corrupted pointer values, resulting in program termination and potential denial of service conditions.
The operational impact of this vulnerability extends beyond simple exploitation scenarios, as it can affect any system running vulnerable versions of Vim when processing swap files from untrusted sources. Attackers can craft malicious swap files that, when opened by Vim during recovery operations, trigger the heap buffer overflow and segmentation fault conditions. This vulnerability is particularly concerning in environments where Vim is used for editing files in shared or collaborative settings, or where automated processes might process swap files from unknown origins. The flaw can be exploited remotely if swap files are transferred through network shares or shared storage systems, making it a significant risk for enterprise environments and development teams that rely on Vim for text editing operations.
The fix implemented in Vim version 9.2.0077 addresses this vulnerability through enhanced validation mechanisms that properly sanitize pointer block fields read from swap files before processing. This remediation aligns with security best practices outlined in common weakness enumeration CWE-121, which covers heap-based buffer overflow conditions, and CWE-125, which addresses out-of-bounds read vulnerabilities. The mitigation strategy follows established cybersecurity frameworks including those referenced in the attack technique ATT&CK matrix under T1059.007 for command and script injection, as the vulnerability could potentially be leveraged to execute malicious code through compromised text editing operations. Organizations should prioritize updating to Vim 9.2.0077 or later versions to eliminate this exposure, while also implementing proper file validation procedures for swap files from untrusted sources. System administrators should consider monitoring for suspicious swap file creation patterns and implement network segmentation controls to limit exposure in environments where Vim is extensively used for collaborative text editing operations.