CVE-2018-16983: NoScript Classic before 5.1.8.7, as used in Tor Browser 7.x and other products, allows attackers to bypass scr

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CRITICAL 9.8REMOTEUPGRADEUPGRADE

CVE-2018-16983 is a critical-severity flaw (CVSS 9.8) affecting noscript, tor browser. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

NoScript Classic before 5.1.8.7, as used in Tor Browser 7.x and other products, allows attackers to bypass script blocking via the text/html;/json Content-Type value.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.1% (top 12%)
CISA exploited list	No
Published	2018-09-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: noscript · torproject

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

Am I affected?

Timeline

2018-09-13 04:29 UTCPublished CVE record published
2026-06-17 01:45 UTCUpdated Record last modified

noscript noscript UPGRADE

Affected: < 5.1.8.7

Fixed in: 5.1.8.7

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 5.1.8.7 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade noscript

Note

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

torproject tor browser UPGRADE

Affected: >= 7.0.0 and <= 7.0.11

Fixed in: newer than 7.0.11

Safe to downgrade to: a release before 7.0.0

1. Check installed version

apt-cache policy tor-browser || rpm -q tor-browser || tor-browser --version

2. UPGRADE to newer than 7.0.11 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade tor-browser

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tor-browser

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 7.0.0 (Debian / Ubuntu)

apt-cache madison tor-browser sudo apt install tor-browser=<VERSION_BEFORE_7.0.0> sudo apt-mark hold tor-browser

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

dnf --showduplicates list tor-browser sudo dnf downgrade tor-browser-<VERSION_BEFORE_7.0.0> sudo dnf versionlock add tor-browser

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-2018-16983?

noscript: upgrade to 5.1.8.7; tor browser: upgrade to newer than 7.0.11. Exact commands for each OS are on this page.

Is CVE-2018-16983 being exploited?

CVE-2018-16983 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-2018-16983 affect?

CVE-2018-16983 affects noscript, tor browser. Severity is critical (CVSS 9.8). NoScript Classic before 5.1.8.7, as used in Tor Browser 7.x and other products, allows attackers to bypass script blocking via the text/html;/json Content-Type value.

How urgent is CVE-2018-16983?

Priority 61/100. Critical severity; Remotely exploitable, no login, no user action

References

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