CVE-2020-3299: Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unau

Q: How do I fix CVE-2020-3299?

secure firewall threat defense: upgrade to 6.3.0.1; snort: upgrade to 2.9.13.1. Exact commands for each OS are on this page.

Q: Is CVE-2020-3299 being exploited?

CVE-2020-3299 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2020-3299 affect?

CVE-2020-3299 affects secure firewall threat defense, snort. Severity is medium (CVSS 5.8). Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured File Policy for HTTP. The vulnerability is due to incorrect detection of modif

Q: How urgent is CVE-2020-3299?

Priority 46/100. Remotely exploitable, no login, no user action

This month

MEDIUM 5.8REMOTEUPGRADEUPGRADE

CVE-2020-3299 is a medium-severity flaw (CVSS 5.8) affecting secure firewall threat defense, snort. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured File Policy for HTTP. The vulnerability is due to incorrect detection of modified HTTP packets used in chunked responses. An attacker could exploit this vulnerability by sending crafted HTTP packets through an affected device. A successful exploit could allow the attacker to bypass a con

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.8 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.3% (top 17%)
CISA exploited list	No
Weakness	CWE-693
Published	2020-10-21
Last modified	2026-08-11

Publisher (CNA): Cisco Systems, Inc. · Vendor: cisco · snort

Last updated 2026-08-11 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-10-21 19:15 UTCPublished CVE record published
2026-08-11 19:33 UTCUpdated Record last modified

cisco secure firewall threat defense UPGRADE

Affected: >= 6.0.0 and < 6.3.0.1

Fixed in: 6.3.0.1

Safe to downgrade to: a release before 6.0.0

1. Check installed version

apt-cache policy secure-firewall-threat-defense || rpm -q secure-firewall-threat-defense || secure-firewall-threat-defense --version

2. UPGRADE to 6.3.0.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade secure-firewall-threat-defense

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade secure-firewall-threat-defense

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 6.0.0 (Debian / Ubuntu)

apt-cache madison secure-firewall-threat-defense sudo apt install secure-firewall-threat-defense=<VERSION_BEFORE_6.0.0> sudo apt-mark hold secure-firewall-threat-defense

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list secure-firewall-threat-defense sudo dnf downgrade secure-firewall-threat-defense-<VERSION_BEFORE_6.0.0> sudo dnf versionlock add secure-firewall-threat-defense

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.

snort snort UPGRADE

Affected: < 2.9.13.1

Fixed in: 2.9.13.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy snort || rpm -q snort || snort --version

2. UPGRADE to 2.9.13.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade snort

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade snort

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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.

Quick answers

How do I fix CVE-2020-3299?

secure firewall threat defense: upgrade to 6.3.0.1; snort: upgrade to 2.9.13.1. Exact commands for each OS are on this page.

Is CVE-2020-3299 being exploited?

CVE-2020-3299 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-2020-3299 affect?

CVE-2020-3299 affects secure firewall threat defense, snort. Severity is medium (CVSS 5.8). Multiple Cisco products are affected by a vulnerability in the Snort detection engine that could allow an unauthenticated, remote attacker to bypass a configured File Policy for HTTP. The vulnerability is due to incorrect detection of modif

How urgent is CVE-2020-3299?

Priority 46/100. Remotely exploitable, no login, no user action

Software pages

Cisco vulnerabilities · Suricata and Snort vulnerabilities

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References

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