PatchTheCVECVE-2013-5661: Cache Poisoning issue exists in DNS Response Rate Limiting.
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MEDIUM 5.9REMOTEWATCHLISTUPGRADEDOWNGRADEUPGRADE
CVE-2013-5661 is a medium-severity flaw (CVSS 5.9) affecting bind, nsd, knot resolver. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Cache Poisoning issue exists in DNS Response Rate Limiting.
Why this priority
- Remotely exploitable, no login, no user action
- On your watchlist
A fixed release or distro patch exists.
Risk facts
| CVSS score | 5.9 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 3.5% (top 11%) |
| CISA exploited list | No |
| Weakness | CWE-290 |
| Published | 2019-11-05 |
| Last modified | 2026-06-16 |
Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
isc bind UPGRADE
Affected: >= 9.8.0 and <= 9.9.0
Fixed in: newer than 9.9.0
Safe to downgrade to: a release before 9.8.0
1. Check installed version
apt-cache policy bind || rpm -q bind || bind --version
2. UPGRADE to newer than 9.9.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade bind
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade bind
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 9.8.0 (Debian / Ubuntu)
apt-cache madison bind
sudo apt install bind=<VERSION_BEFORE_9.8.0>
sudo apt-mark hold bind
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list bind
sudo dnf downgrade bind-<VERSION_BEFORE_9.8.0>
sudo dnf versionlock add bind
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
nlnetlabs nsd DOWNGRADE
Affected: 3.2.15
Fixed in: no fixed release known
Safe to downgrade to: a release before 3.2.15
1. Check installed version
apt-cache policy nsd || rpm -q nsd || nsd --version
2. No fixed release: DOWNGRADE to a release before 3.2.15 (Debian / Ubuntu)
apt-cache madison nsd
sudo apt install nsd=<VERSION_BEFORE_3.2.15>
sudo apt-mark hold nsd
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list nsd
sudo dnf downgrade nsd-<VERSION_BEFORE_3.2.15>
sudo dnf versionlock add nsd
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
nic knot resolver UPGRADE
Affected: < 1.3.0
Fixed in: 1.3.0
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy knot-resolver || rpm -q knot-resolver || knot-resolver --version
2. UPGRADE to 1.3.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade knot-resolver
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade knot-resolver
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
redhat enterprise linux MITIGATE
Affected: 6.0 · 7.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 6.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2013-5661?
bind: upgrade to newer than 9.9.0; nsd: downgrade or apply the listed mitigation; knot resolver: upgrade to 1.3.0. Exact commands for each OS are on this page.
Is CVE-2013-5661 being exploited?
CVE-2013-5661 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2013-5661 affect?
CVE-2013-5661 affects bind, nsd, knot resolver. Severity is medium (CVSS 5.9). Cache Poisoning issue exists in DNS Response Rate Limiting.
How urgent is CVE-2013-5661?
Priority 53/100. Remotely exploitable, no login, no user action; On your watchlist
Software pages
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