● Medium · CVSS 4.8

How to Fix CVE-2026-2869: Out-of-bounds read in janet

Q: What is the CVSS score for CVE-2026-2869?

4.8 (Medium). Vector: `CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`.

Q: Where is the official advisory for CVE-2026-2869?

The vendor advisory is at [https://vuldb.com/?id.347106](https://vuldb.com/?id.347106). The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-2869.

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

CVE-2026-2869 is a out-of-bounds read in janet-lang janet. The fix is to upgrade to janet 1.41.0.

⚡ At a glance


Severity	4.8 (Medium)
Actively exploited?	No public listing in CISA KEV
Affected	janet 1.40.0; janet 1.40.1
Fixed in	janet 1.41.0
Type (CWE)	CWE-125: Out-of-Bounds Read

What is CVE-2026-2869?

A vulnerability was identified in janet-lang janet up to 1.40.1. Affected by this vulnerability is the function janetc_varset of the file src/core/specials.c of the component handleattr Handler. The manipulation leads to out-of-bounds read. The attack can only be performed from a local environment. The exploit is publicly available and might be used. Upgrading to version 1.41.0 addresses this issue. The identifier of the patch is 2fabc80151a2b8834ee59cda8a70453f848b40e5. The affected component should be upgraded. The CVSS base score is 4.8 (Medium). The official advisory is at https://vuldb.com/?id.347106.

Am I affected?

Check the version of janet you are running and compare it against the Affected row above (janet 1.40.0; janet 1.40.1). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:


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


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

How to fix CVE-2026-2869

Upgrade janet to a patched build: janet 1.41.0. 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 janet
dpkg -s janet | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux


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

SUSE / openSUSE


sudo zypper refresh
sudo zypper update janet
rpm -q janet

Node.js / npm


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

Complete PowerShell remediation script (Windows)


# Fix script for CVE-2026-2869 affecting janet
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-2869-fix-$(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"
    $pkg = Get-Package -Name "*janet*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

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

    Write-Host "[3/4] Apply the upgrade to janet 1.41.0"
    winget upgrade --name "janet" --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 "janet"
    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-2026-2869 affecting janet
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-2869-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 janet 2>/dev/null | grep -i ^Version || echo "janet not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q janet || echo "janet not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-2869-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/janet /etc/janet.d /etc/janet.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Apply the upgrade (target: janet 1.41.0)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y janet
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y janet
elif command -v yum >/dev/null; then
    yum update -y janet
elif command -v zypper >/dev/null; then
    zypper --non-interactive update janet
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s janet 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q janet
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-2026-2869" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-2869"

Disable the affected service (Linux)


sudo systemctl stop janet 2>/dev/null || true
sudo systemctl disable janet 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 janet 2>/dev/null | grep -i ^Version
rpm -q janet 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 "*janet*" | Select-Object Name, Version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above janet 1.41.0. 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:

How to Fix CVE-2026-1719: Improper Neutralization of Special Elements used in an SQL Command ('SQL Injecti — Improper Neutralization of Special Elements used in an SQL Command ('SQL Injecti
How to Fix CVE-2026-3955: elecV2P jsfile Endpoint wbjs.js runJSFile code injection in elecV2P — elecV2P jsfile Endpoint wbjs.js runJSFile code injection in elecV2P
How to Fix CVE-2026-3809: Tenda FH1202 NatSaticSetting fromNatStaticSetting stack-based overflow , Tenda FH1202 NatSaticSetting fromNatStaticSetting stack-based overflow
How to Fix CVE-2026-26009: Command Injection in catalyst , Command Injection in catalyst
How to Fix CVE-2026-4826: SQL Injection in Sales and Inventory System , SQL Injection in Sales and Inventory System

Is CVE-2026-2869 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-2026-2869?

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-2026-2869?

4.8 (Medium). Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P.

Where is the official advisory for CVE-2026-2869?

The vendor advisory is at https://vuldb.com/?id.347106. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-2869.

References

Official vendor advisory: https://vuldb.com/?id.347106
NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2869
CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Additional reference: https://vuldb.com/?ctiid.347106
Additional reference: https://vuldb.com/?submit.754589
Additional reference: https://github.com/janet-lang/janet/issues/1699

*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.*