CVE-2025-20359: Multiple Cisco products are affected by a vulnerability in the Snort 3 HTTP Decoder that could allow an unauth

Routine

MEDIUM 6.5REMOTEUPGRADE

CVE-2025-20359 is a medium-severity flaw (CVSS 6.5) affecting 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 3 HTTP Decoder that could allow an unauthenticated, remote attacker to cause the disclosure of possible sensitive data or cause the Snort 3 Detection Engine to crash. This vulnerability is due to an error in the logic of buffer handling when the MIME fields of the HTTP header are parsed. This can result in a buffer under-read. An attacker could exploit this vulnerability by s

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 59%)
CISA exploited list	No
Weakness	CWE-127
Published	2025-10-15
Last modified	2026-10-18

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

Last updated 2026-10-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-10-15 17:15 UTCPublished CVE record published
2026-10-18 21:10 UTCUpdated Record last modified

cisco snort UPGRADE

Affected: >= 3.0.0-233 and < 3.9.3.0

Fixed in: 3.9.3.0

Safe to downgrade to: a release before 3.0.0-233

1. Check installed version

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

2. UPGRADE to 3.9.3.0 (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.

3. If no update is available yet, DOWNGRADE to a release before 3.0.0-233 (Debian / Ubuntu)

apt-cache madison snort sudo apt install snort=<VERSION_BEFORE_3.0.0-233> sudo apt-mark hold snort

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

dnf --showduplicates list snort sudo dnf downgrade snort-<VERSION_BEFORE_3.0.0-233> sudo dnf versionlock add snort

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.

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-2025-20359?

snort: upgrade to 3.9.3.0. Exact commands for each OS are on this page.

Is CVE-2025-20359 being exploited?

CVE-2025-20359 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-2025-20359 affect?

CVE-2025-20359 affects snort. Severity is medium (CVSS 6.5). Multiple Cisco products are affected by a vulnerability in the Snort 3 HTTP Decoder that could allow an unauthenticated, remote attacker to cause the disclosure of possible sensitive data or cause the Snort 3 Detection Engine to crash. T

How urgent is CVE-2025-20359?

Priority 38/100. Remotely exploitable, no login, no user action

Software pages

Cisco vulnerabilities · Suricata and Snort vulnerabilities

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References

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