⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 5.5

How to Fix CVE-2026-27117: Path traversal in bit7z

By Sai Kiran Pandrala. Last verified: 2026-05-25.

CVE-2026-27117 is a path traversal in rikyoz bit7z. The fix is to apply the vendor patch noted below.

⚡ At a glance
Severity5.5 (Medium)
Actively exploited?No public listing in CISA KEV
Affectedbit7z < 4.0.11
Fixed inSee vendor advisory
Type (CWE)CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

What is CVE-2026-27117?

bit7z is a cross-platform C++ static library that allows the compression/extraction of archive files. Prior to version 4.0.11, a path traversal vulnerability ("Zip Slip") exists in bit7z's archive extraction functionality. The library does not adequately validate file paths contained in archive entries, allowing files to be written outside the intended extraction directory through three distinct mechanisms: relative path traversal, absolute path traversal, and symbolic link traversal. An attacker can exploit this by providing a malicious archive to any application that uses bit7z to extract untrusted archives. Successful exploitation results in arbitrary file write with the privileges of the process performing the extraction. This could lead to overwriting of application binaries, configuration files, or other sensitive data. The vulnerability does not directly enable reading of file contents; the confidentiality impact is limited to the calling application's own behavior after extraction. However, applications that subsequently serve or display extracted files may face secondary confidentiality risks from attacker-created symlinks. Fixes have been released in version 4.0.11. If upgrading is not immediately possible, users can mitigate the vulnerability by validating each entry's destination path before writing. Other mitigations include running extraction with least privilege and extracting untrusted archives in a sandboxed directory. The CVSS base score is 5.5 (Medium). The official advisory is at https://github.com/rikyoz/bit7z/security/advisories/GHSA-qvjh-hhw4-3gx9.

Am I affected?

Check the version of bit7z you are running and compare it against the Affected row above (bit7z < 4.0.11). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:


# Linux package check
dpkg -s bit7z 2>/dev/null | grep -i ^Version
rpm -q bit7z 2>/dev/null
command -v bit7z >/dev/null && bit7z --version 2>/dev/null


# Windows (PowerShell)
Get-Package -Name "*bit7z*" -ErrorAction SilentlyContinue | Select-Object Name, Version
winget list --name "bit7z" 2>$null

How to fix CVE-2026-27117

Upgrade bit7z to a patched build: See vendor advisory. The vendor advisory is the source of truth for the exact fixed version.

Ubuntu / Debian


sudo apt-get update
sudo apt-get install --only-upgrade bit7z
dpkg -s bit7z | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux


sudo dnf upgrade --refresh bit7z -y
# or for older releases:
sudo yum update bit7z -y
rpm -q bit7z

SUSE / openSUSE


sudo zypper refresh
sudo zypper update bit7z
rpm -q bit7z

Node.js / npm


# Update the affected package in your project
npm install bit7z@latest
npm ls bit7z
npm audit fix

Complete PowerShell remediation script (Windows)


# Fix script for CVE-2026-27117 affecting bit7z
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-27117-fix-$(Get-Date -Format yyyyMMdd-HHmmss).log"
New-Item -ItemType Directory -Force (Split-Path $LogPath) | Out-Null
Start-Transcript -Path $LogPath -Append

try {
    Write-Host "[1/4] Detect installed version"
    $pkg = Get-Package -Name "*bit7z*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

    Write-Host "[2/4] Backup configuration"
    $backup = "C:\Backup\bit7z-$(Get-Date -Format yyyyMMdd)"
    New-Item -ItemType Directory -Force $backup | Out-Null
    Get-ChildItem "C:\ProgramData\bit7z" -ErrorAction SilentlyContinue |
        Copy-Item -Destination $backup -Recurse -Force -ErrorAction SilentlyContinue

    Write-Host "[3/4] Apply the upgrade to See vendor advisory"
    winget upgrade --name "bit7z" --silent --accept-source-agreements --accept-package-agreements
    if ($LASTEXITCODE -ne 0) {
        # Fallback: pull latest via OS update channel
        Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -ErrorAction SilentlyContinue
        Import-Module PSWindowsUpdate
        Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot
    }

    Write-Host "[4/4] Verify the patched build"
    winget list --name "bit7z"
    Write-Host "Patch applied. Reboot if prompted."
    exit 0
} catch {
    Write-Error "Patch failed: $_"
    exit 1
} finally {
    Stop-Transcript
}

Complete Bash remediation script (Linux)


#!/usr/bin/env bash
# Fix script for CVE-2026-27117 affecting bit7z
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-27117-fix-$(date +%Y%m%d-%H%M%S).log"
exec > >(tee -a "$LOG") 2>&1

echo "[1/4] Detect installed version"
if command -v dpkg >/dev/null; then
    dpkg -s bit7z 2>/dev/null | grep -i ^Version || echo "bit7z not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q bit7z || echo "bit7z not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-27117-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/bit7z /etc/bit7z.d /etc/bit7z.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Apply the upgrade (target: See vendor advisory)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y bit7z
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y bit7z
elif command -v yum >/dev/null; then
    yum update -y bit7z
elif command -v zypper >/dev/null; then
    zypper --non-interactive update bit7z
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s bit7z 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q bit7z
fi
echo "Done. Restart any service that loaded the old library."

If you can't patch immediately

Apply at least one of the following inline controls until you can deploy the patched build. None replace the upgrade.

Restrict exposure with nftables (Linux)


# Allow only trusted CIDR to reach the affected service ports
sudo nft add table inet filter 2>/dev/null || true
sudo nft 'add chain inet filter input { type filter hook input priority 0 ; }' 2>/dev/null || true
sudo nft 'add rule inet filter input tcp dport {80, 443} ip saddr != 10.0.0.0/8 drop'
sudo nft list ruleset

Block at the host firewall (Windows)


New-NetFirewallRule -DisplayName "Block-CVE-2026-27117" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-27117"

Disable the affected service (Linux)


sudo systemctl stop bit7z 2>/dev/null || true
sudo systemctl disable bit7z 2>/dev/null || true

If the vendor advisory lists an official workaround, prefer that wording verbatim. If no workaround is published, the only safe remediation is the patch.

How to verify the fix worked

After upgrading, confirm the installed version matches the patched build and that no old library is still loaded by a long-running process.


# Linux
dpkg -s bit7z 2>/dev/null | grep -i ^Version
rpm -q bit7z 2>/dev/null || true
# Pid map check for old library handles
sudo lsof +c0 2>/dev/null | grep -i "DEL.*lib" || true


# Windows
Get-Package -Name "*bit7z*" | Select-Object Name, Version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above See vendor advisory. Restart the affected service (systemctl restart <service> on Linux, or restart the Windows service) so it loads the patched binary.

Frequently asked questions

Other vulnerabilities in the same area that are worth patching alongside this one:

Is CVE-2026-27117 actively exploited?

There is no public confirmation of exploitation in the wild listed in CISA KEV at the time of this writing. Patch anyway. Public exploits commonly follow disclosure within weeks.

Do I need to reboot after patching CVE-2026-27117?

For kernel and OS-level updates, yes. For most userland packages a systemctl restart <service> is enough on Linux, and restarting the Windows service or app on Windows. Any process that loaded the old library keeps using it until restarted.

What is the CVSS score for CVE-2026-27117?

5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N.

Where is the official advisory for CVE-2026-27117?

The vendor advisory is at https://github.com/rikyoz/bit7z/security/advisories/GHSA-qvjh-hhw4-3gx9. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-27117.

References

*Written by Sai Kiran Pandrala. Assembled from the official vendor advisory, NVD record, and CISA KEV listing on 2026-05-25. Always confirm against the vendor's advisory before applying changes in production.*