CVE-2026-6985: A weakness has been identified in Cesanta Mongoose up to 7.20

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MEDIUM 5.3REMOTEUPGRADE

CVE-2026-6985 is a medium-severity flaw (CVSS 5.3) affecting mongoose. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the file /src/net_builtin.c of the component TCP Option Handler. This manipulation of the argument optlen causes infinite loop. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 7.21 is able to resolve this issue. Upgrading the af

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-404, CWE-835
Published	2026-04-25
Last modified	2026-10-26

Publisher (CNA): VulDB · Vendor: cesanta

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-25 17:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

cesanta mongoose UPGRADE

Affected: >= 7.0 and < 7.21

Fixed in: 7.21

Safe to downgrade to: a release before 7.0

1. Check installed version

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

2. UPGRADE to 7.21 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mongoose

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 7.0 (Debian / Ubuntu)

apt-cache madison mongoose sudo apt install mongoose=<VERSION_BEFORE_7.0> sudo apt-mark hold mongoose

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

dnf --showduplicates list mongoose sudo dnf downgrade mongoose-<VERSION_BEFORE_7.0> sudo dnf versionlock add mongoose

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-2026-6985?

mongoose: upgrade to 7.21. Exact commands for each OS are on this page.

Is CVE-2026-6985 being exploited?

CVE-2026-6985 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-2026-6985 affect?

CVE-2026-6985 affects mongoose. Severity is medium (CVSS 5.3). A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the file /src/net_builtin.c of the component TCP Option Handler. This manipulation of the argument optlen causes infinite l

How urgent is CVE-2026-6985?

Priority 40/100. Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-5244 HIGH 7.3 UPGRADE A vulnerability has been found in Cesanta Mongoose up to 7.20
CVE-2026-5246 MEDIUM 5.6 UPGRADE A vulnerability was determined in Cesanta Mongoose up to 7.20
CVE-2026-5245 MEDIUM 5.6 UPGRADE A vulnerability was found in Cesanta Mongoose up to 7.20
CVE-2026-6986 LOW 3.7 UPGRADE A security vulnerability has been detected in Cesanta Mongoose up to 7.20
CVE-2026-42334 HIGH 7.5 UPGRADE Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment

References

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