CVE-2021-35440: Smashing 1.3.4 is vulnerable to Cross Site Scripting (XSS)

Routine

MEDIUM 6.1DOWNGRADE

CVE-2021-35440 is a medium-severity flaw (CVSS 6.1) affecting smashing. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Smashing 1.3.4 is vulnerable to Cross Site Scripting (XSS). A URL for a widget can be crafted and used to execute JavaScript on the victim's computer. The JavaScript code can then steal data available in the session/cookies depending on the user environment (e.g. if re-using internal URL's for deploying, or cookies that are very permissive) private information may be retrieved by the attacker.

Why this priority

No elevated risk signals yet

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-07-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: smashing project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-07-06 15:15 UTCPublished CVE record published
2026-06-17 03:57 UTCUpdated Record last modified

smashing project smashing DOWNGRADE

Affected: 1.3.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.3.4

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 1.3.4 (Debian / Ubuntu)

apt-cache madison smashing sudo apt install smashing=<VERSION_BEFORE_1.3.4> sudo apt-mark hold smashing

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list smashing sudo dnf downgrade smashing-<VERSION_BEFORE_1.3.4> sudo dnf versionlock add smashing

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-2021-35440?

smashing: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-35440 being exploited?

CVE-2021-35440 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-2021-35440 affect?

CVE-2021-35440 affects smashing. Severity is medium (CVSS 6.1). Smashing 1.3.4 is vulnerable to Cross Site Scripting (XSS). A URL for a widget can be crafted and used to execute JavaScript on the victim's computer. The JavaScript code can then steal data available in the session/cookies depending on the

How urgent is CVE-2021-35440?

Priority 37/100. No elevated risk signals yet.

References

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