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Improper Link Resolution Before File Access ('Link Following')

CVE-2026-23879

High
8/10

Summary

There exists an **arbitrary file write vulnerability** in `py7zr` prior to 1.1.3, which allows symbolic links to be recreated outside the destination directory via crafted malicious symbolic link chains. When using `extractall` to extract an archive, the library restores these symbolic links, linking them to arbitrary directories on the host file system. Subsequent extraction of regular files through these symbolic links can result in arbitrary file writes. This vulnerability may lead to remote code execution, privilege escalation, data corruption, or denial of service.

  • LOW
  • NETWORK
  • HIGH
  • UNCHANGED
  • REQUIRED
  • LOW
  • HIGH
  • HIGH

CWE-59 - Improper Link Resolution Before File Access

'Improper link resolution before file access' occurs when software accesses a file resource but fails to verify that the file isn't a link or shortcut to another file. An attacker can potentially gain access to arbitrary files and from there the impact can vary, depending on the application, from sensitive data exposure to remote code execution.

References

Advisory Timeline

  • Published