CVE-2026-71267
Description
A flaw was found in microtar. The mtar_write_file_header() and mtar_write_dir_header() functions copy a caller-supplied entry name into a fixed 100-byte stack buffer using strcpy() without validating the name length. An application that archives an attacker-controlled or externally supplied filename longer than 99 characters can trigger a stack buffer overflow, which could lead to arbitrary code execution or denial of service.
Statement
This Important flaw in microtar allows a stack buffer overflow when applications process externally-influenced filenames exceeding 99 characters. Exploitation could lead to a denial of service or potentially arbitrary code execution if an application using microtar archives attacker-controlled input without proper validation.
Red Hat rates this issue with User Interaction Required (UI:R). Exploitation depends on an application using microtar to archive a caller-supplied entry name longer than 99 characters. That path typically needs a user or application action that supplies the filename, rather than a fully automated remote attack with no interaction. The CNA assessment uses UI:N; Red Hat's score reflects this precondition.
Mitigation
No practical library-level workaround or fixed upstream release is published;
all versions are reported affected. Applications that embed microtar should
reject or truncate entry names to fewer than 100 bytes before calling
mtar_write_file_header() / mtar_write_dir_header(), or replace microtar with a
maintained tar implementation. Until a patched microtar is available, avoid
archiving untrusted or attacker-controlled filenames with this library.
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of the product's implicit security policy. This can often be used to subvert any other security service.
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the product into an infinite loop.
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