CVE-2024-43802 in vim
Summary
by MITRE • 08/26/2024
Vim is an improved version of the unix vi text editor. When flushing the typeahead buffer, Vim moves the current position in the typeahead buffer but does not check whether there is enough space left in the buffer to handle the next characters. So this may lead to the tb_off position within the typebuf variable to point outside of the valid buffer size, which can then later lead to a heap-buffer overflow in e.g. ins_typebuf(). Therefore, when flushing the typeahead buffer, check if there is enough space left before advancing the off position. If not, fall back to flush current typebuf contents. It's not quite clear yet, what can lead to this situation. It seems to happen when error messages occur (which will cause Vim to flush the typeahead buffer) in comnination with several long mappgins and so it may eventually move the off position out of a valid buffer size. Impact is low since it is not easily reproducible and requires to have several mappings active and run into some error condition. But when this happens, this will cause a crash. The issue has been fixed as of Vim patch v9.1.0697. Users are advised to upgrade. There are no known workarounds for this issue.
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Analysis
by VulDB Data Team • 01/21/2026
The vulnerability identified as CVE-2024-43802 affects the Vim text editor, specifically within its typeahead buffer handling mechanism. This flaw resides in the buffer management logic where Vim fails to validate available space before advancing the typeahead buffer offset position. The issue manifests when Vim attempts to flush the typeahead buffer during error conditions, particularly when multiple long mappings are active. The root cause can be traced to CWE-129, which addresses insufficient boundary checking in buffer operations, and more specifically to CWE-121, concerning buffer overflow conditions due to improper memory management. The vulnerability represents a heap-buffer overflow scenario that occurs in the ins_typebuf() function when the tb_off position within the typebuf variable extends beyond the valid buffer boundaries.
The operational impact of this vulnerability stems from its potential to cause application crashes during normal editing operations. When error messages trigger the typeahead buffer flushing process, the combination of active long mappings and error conditions can push the buffer offset beyond acceptable limits. This creates a condition where subsequent buffer operations attempt to access memory locations outside the allocated heap space, resulting in unpredictable behavior and system instability. The ATT&CK framework categorizes this as a privilege escalation vector through application crash, specifically under T1499.004 for Virtualization/Sandbox Evasion, though in this case it manifests as a denial of service through crash conditions rather than malicious exploitation. The low reproducibility factor makes this vulnerability particularly concerning as it may remain undetected until specific error conditions are met, potentially leading to unexpected application termination.
Mitigation strategies for CVE-2024-43802 center exclusively on upgrading to Vim version 9.1.0697 or later, which contains the necessary patch to address the buffer overflow condition. The fix implements proper bounds checking before advancing the typeahead buffer offset, ensuring that the tb_off position remains within valid buffer limits before any buffer advancement occurs. Organizations should prioritize this update across all systems where Vim is deployed, particularly in environments where automated scripts or continuous editing sessions might trigger the error conditions that expose this vulnerability. Security teams should monitor for potential exploitation attempts that might leverage this vulnerability in combination with other attack vectors, though the current assessment indicates that the exploitability remains limited due to the specific combination of conditions required to trigger the flaw. The absence of known workarounds means that defensive measures must rely entirely on patch management procedures and system updates rather than configuration changes or temporary fixes.