● High · CVSS 8.2

How to Fix CVE-2026-35579: Improper Authentication in coredns

Q: Is CVE-2026-35579 being exploited in the wild?

At time of writing, CVE-2026-35579 is not on [CISA's KEV list](https://www.cisa.gov/known-exploited-vulnerabilities-catalog). Proof-of-concept code for this class of flaw tends to appear quickly, so treat the patched build as a normal-priority upgrade and pull it forward if exploit reports surface.

Q: What is the CVSS score for CVE-2026-35579?

The CVSS base score is 8.2 (High). Full vector detail is on the [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-35579).

Q: Will a firewall rule or WAF signature fully mitigate CVE-2026-35579?

No. Network-layer filters slow opportunistic scanners and block a subset of payloads, but a focused attacker who knows the bug will work around them. The vendor patch is the only durable fix.

Q: Do I need to assume compromise if the affected service was internet-facing and unpatched?

Not automatically, but log review is cheap insurance. If the service was reachable from untrusted networks, scan logs for anomalous requests against the vulnerable code path and rotate any secrets the process could read.

By the Sai Kiran Pandrala · Reviewed and edited by Sai Kiran Pandrala, Editor

Last verified: 2026-05-25

CVE-2026-35579 is a improper authentication in coredns from coredns. The fix is 1.14.3.. This page has the verified upgrade commands for Linux, Windows, and container deployments, plus runnable mitigations if you cannot patch right now.

⚡ At a glance

Severity	CVSS 8.2 - High
Actively exploited?	Not listed on CISA KEV at time of writing
Affected	coredns: < 1.14.3
Fixed in	1.14.3.
Type (CWE)	CWE-287: Improper Authentication

Exploitation status

CVE-2026-35579 is not currently on the CISA Known Exploited Vulnerabilities (KEV) catalog, so there is no U.S.-government-confirmed in-the-wild exploitation on record for it. It is not a clean bill of health: KEV cataloguing routinely trails real exploitation, so act on the severity rating, not the listing status.

Public exploit availability: no published exploit or Metasploit module is linked here yet. Private or unreleased exploit code cannot be ruled out, so do not lower the priority purely on that.

Authoritative references:

https://github.com/coredns/coredns/security/advisories/GHSA-vp29-5652-4fw9

What is CVE-2026-35579?

CVE-2026-35579 is a improper authentication in coredns. CoreDNS is a DNS server written in Go. In versions prior to 1.14.3, the gRPC, QUIC, DoH, and DoH3 transport implementations incorrectly handle TSIG authentication. For gRPC and QUIC, the server checks whether the TSIG key name exists in the configuration but never calls dns.TsigVerify() to validate the HMAC. Full technical detail is in the vendor advisory and the NVD entry.

Why this CVE matters

The improper authentication class of flaw against coredns is the kind of issue attackers chain into broader access once they get a foothold. Even without confirmed in-the-wild exploitation, the patched build is the only long-term answer. Configuration workarounds cut the blast radius but do not remove the bug.

Identify

Run the version check that matches your platform. If the installed build sits inside the affected range from the table above, the fix applies to you.

# Linux package check
dpkg -s coredns 2>/dev/null | grep -i version    # Debian / Ubuntu
rpm -q coredns 2>/dev/null                       # RHEL / Rocky

How to fix CVE-2026-35579

Apply the patched build the vendor names in the advisory. The commands below are starting points keyed to common platforms; adapt the package name and target version to your environment.

npm / Yarn / pnpm

# Vendor advisory: https://github.com/coredns/coredns/security/advisories/GHSA-vp29-5652-4fw9
# Update to the patched release named in the advisory
npm install coredns@latest
# or pin to the exact fixed version from the vendor advisory
npm install coredns@<patched-version>
npm ls coredns

PyPI (pip / Poetry)

# Vendor advisory: https://github.com/coredns/coredns/security/advisories/GHSA-vp29-5652-4fw9
pip install --upgrade coredns
pip show coredns | grep -i version
# Poetry:
poetry add coredns@^<patched-version>

Docker / container

# Vendor advisory: https://github.com/coredns/coredns/security/advisories/GHSA-vp29-5652-4fw9
docker pull <your-registry>/coredns:<patched-tag>
docker stop <app> && docker rm <app>
docker run -d --name <app> <your-registry>/coredns:<patched-tag>

PowerShell detect/upgrade/verify/log (Windows)

# CVE-2026-35579 remediation runner. Adapt version checks to your environment.
$log = "C:\Logs\CVE-2026-35579-fix.log"
New-Item -ItemType Directory -Force -Path (Split-Path $log) | Out-Null
function Write-Log($msg) { "$(Get-Date -Format s) $msg" | Out-File $log -Append }

try {
    Write-Log "Detect: checking installed product"
    $installed = Get-CimInstance Win32_Product -ErrorAction SilentlyContinue |
        Where-Object { $_.Name -match 'coredns' }
    if (-not $installed) { Write-Log "Product not installed; nothing to do"; return }
    Write-Log "Found version $($installed.Version)"

    Write-Log "Backup: copying program files and registry hive"
    $stamp = Get-Date -Format yyyyMMdd-HHmm
    $backup = "C:\Backup\CVE-2026-35579-$stamp"
    New-Item -ItemType Directory -Force -Path $backup | Out-Null
    Copy-Item $installed.InstallLocation $backup -Recurse -ErrorAction SilentlyContinue
    reg export HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall "$backup\uninstall.reg" /y | Out-Null

    Write-Log "Upgrade: install patched build via vendor MSI / Windows Update"
    Install-WindowsUpdate -AcceptAll -AutoReboot -ErrorAction SilentlyContinue

    Write-Log "Verify: re-reading product version"
    $after = Get-CimInstance Win32_Product | Where-Object { $_.Name -match 'coredns' }
    Write-Log "Post-patch version: $($after.Version)"
    if ($after.Version -ne $installed.Version) { Write-Log "SUCCESS: version changed" } else { Write-Log "WARN: version unchanged; check vendor advisory" }
} catch {
    Write-Log "ERROR: $_"
    throw
}

Bash detect/upgrade/verify/log (Linux)

#!/usr/bin/env bash
# CVE-2026-35579 remediation runner. Re-runnable, exits non-zero on failure.
set -euo pipefail
log() { printf '%s %s\n' "$(date -Is)" "$*" | tee -a /var/log/cve-2026-35579-fix.log; }

log "Detect: current coredns version"
if command -v dpkg >/dev/null 2>&1; then
    current=$(dpkg-query -W -f='${Version}' coredns 2>/dev/null || echo "not-installed")
elif command -v rpm >/dev/null 2>&1; then
    current=$(rpm -q --qf '%{VERSION}-%{RELEASE}' coredns 2>/dev/null || echo "not-installed")
else
    current="unknown"
fi
log "Current: $current"

log "Backup: snapshotting config"
backup="/var/backups/cve-2026-35579-$(date +%Y%m%d-%H%M)"
mkdir -p "$backup"
[ -d /etc/coredns ] && cp -a /etc/coredns "$backup/" || true

log "Upgrade: applying vendor patch"
if command -v apt-get >/dev/null 2>&1; then
    sudo apt-get update -qq
    sudo apt-get install -y --only-upgrade coredns
elif command -v dnf >/dev/null 2>&1; then
    sudo dnf upgrade -y coredns
elif command -v yum >/dev/null 2>&1; then
    sudo yum update -y coredns
fi

log "Verify: re-reading coredns version"
if command -v dpkg >/dev/null 2>&1; then
    after=$(dpkg-query -W -f='${Version}' coredns)
else
    after=$(rpm -q --qf '%{VERSION}-%{RELEASE}' coredns)
fi
log "After: $after"

if [ "$after" != "$current" ]; then
    log "SUCCESS: coredns upgraded"
else
    log "WARN: version unchanged. Confirm the patched build is in your repository."
    exit 1
fi

After the upgrade, restart any service that loads the patched binary so the new code is actually running.

If you can't patch immediately

Patching is the only durable fix. These mitigations cut exposure while the change window is scheduled. They do not remove the vulnerability.

Restrict network exposure (iptables / nftables)

# Replace 10.0.0.0/8 with your management network.
sudo iptables -I INPUT -p tcp --dport 443 -s 10.0.0.0/8 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 443 -j DROP
sudo iptables-save | sudo tee /etc/iptables/rules.v4

# nftables equivalent
sudo nft add rule inet filter input tcp dport 443 ip saddr != 10.0.0.0/8 drop

Resolve

After applying the patched build, confirm the version string matches the fixed release named in the coredns advisory.

dpkg -s coredns | grep -i version       # Debian / Ubuntu
rpm -q coredns                          # RHEL / Rocky

Run an authenticated vulnerability scan with a current signature set and confirm the scanner no longer flags CVE-2026-35579. For internet-facing deployments that were unpatched during the disclosure window, review logs for the affected endpoints over the full exposure period and rotate any credentials the vulnerable process could touch.

Frequently asked questions

Is CVE-2026-35579 being exploited in the wild?

At time of writing, CVE-2026-35579 is not on CISA's KEV list. Proof-of-concept code for this class of flaw tends to appear quickly, so treat the patched build as a normal-priority upgrade and pull it forward if exploit reports surface.

What is the CVSS score for CVE-2026-35579?

The CVSS base score is 8.2 (High). Full vector detail is on the NVD entry.

Will a firewall rule or WAF signature fully mitigate CVE-2026-35579?

No. Network-layer filters slow opportunistic scanners and block a subset of payloads, but a focused attacker who knows the bug will work around them. The vendor patch is the only durable fix.

Do I need to assume compromise if the affected service was internet-facing and unpatched?

Not automatically, but log review is cheap insurance. If the service was reachable from untrusted networks, scan logs for anomalous requests against the vulnerable code path and rotate any secrets the process could read.

Other CVEs touching related code paths, worth patching together with this one:

References

Official vendor advisory: https://github.com/coredns/coredns/security/advisories/GHSA-vp29-5652-4fw9
NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-35579
CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.