● Medium · CVSS 4.8

How to Fix CVE-2026-2887: Uncontrolled recursion in lobster

Q: What is the CVSS score for CVE-2026-2887?

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-2026-2887?

The vendor advisory is at [https://vuldb.com/?id.347181](https://vuldb.com/?id.347181). The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-2887.

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

CVE-2026-2887 is a uncontrolled recursion in aardappel lobster. The fix is to upgrade to lobster 2026.1.

⚡ At a glance


Severity	4.8 (Medium)
Actively exploited?	No public listing in CISA KEV
Affected	lobster 2025.0; lobster 2025.1; lobster 2025.2; lobster 2025.3; lobster 2025.4
Fixed in	lobster 2026.1
Type (CWE)	CWE-674: Uncontrolled Recursion

What is CVE-2026-2887?

A security vulnerability has been detected in aardappel lobster up to 2025.4. This impacts the function lobster::TypeName in the library dev/src/lobster/idents.h. Such manipulation leads to uncontrolled recursion. The attack can only be performed from a local environment. The exploit has been disclosed publicly and may be used. Upgrading to version 2026.1 will fix this issue. The name of the patch is 8ba49f98ccfc9734ef352146806433a41d9f9aa6. It is advisable to upgrade the affected component. The CVSS base score is 4.8 (Medium). The official advisory is at https://vuldb.com/?id.347181.

Am I affected?

Check the version of lobster you are running and compare it against the Affected row above (lobster 2025.0; lobster 2025.1; lobster 2025.2; lobster 2025.3; lobster 2025.4). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:


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


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

How to fix CVE-2026-2887

Upgrade lobster to a patched build: lobster 2026.1. 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 lobster
dpkg -s lobster | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux


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

SUSE / openSUSE


sudo zypper refresh
sudo zypper update lobster
rpm -q lobster

Node.js / npm


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

Complete PowerShell remediation script (Windows)


# Fix script for CVE-2026-2887 affecting lobster
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-2887-fix-$(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"
    $pkg = Get-Package -Name "*lobster*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

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

    Write-Host "[3/4] Apply the upgrade to lobster 2026.1"
    winget upgrade --name "lobster" --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 "lobster"
    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-2026-2887 affecting lobster
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-2887-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 lobster 2>/dev/null | grep -i ^Version || echo "lobster not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q lobster || echo "lobster not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-2887-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/lobster /etc/lobster.d /etc/lobster.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Apply the upgrade (target: lobster 2026.1)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y lobster
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y lobster
elif command -v yum >/dev/null; then
    yum update -y lobster
elif command -v zypper >/dev/null; then
    zypper --non-interactive update lobster
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s lobster 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q lobster
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-2026-2887" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-2887"

Disable the affected service (Linux)


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

Expected: the reported version is at or above lobster 2026.1. Restart the affected service (systemctl restart <service> on Linux, or restart the Windows service) so it loads the patched binary.

Frequently asked questions

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Is CVE-2026-2887 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-2026-2887?

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-2026-2887?

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-2026-2887?

The vendor advisory is at https://vuldb.com/?id.347181. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-2887.

References

Official vendor advisory: https://vuldb.com/?id.347181
NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2887
CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Additional reference: https://vuldb.com/?ctiid.347181
Additional reference: https://vuldb.com/?submit.755026
Additional reference: https://github.com/aardappel/lobster/issues/397

*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.*