CVE-2021-42342: An issue was discovered in GoAhead 4.x and 5.x before 5.1.5

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-42342 is a critical-severity flaw (CVSS 9.8) affecting goahead. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in GoAhead 4.x and 5.x before 5.1.5. In the file upload filter, user form variables can be passed to CGI scripts without being prefixed with the CGI prefix. This permits tunneling untrusted environment variables into vulnerable CGI scripts.

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
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	59.5% (top 1%)
CISA exploited list	No
Weakness	CWE-434
Published	2021-10-14
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: embedthis

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

Am I affected?

Timeline

2021-10-14 06:15 UTCPublished CVE record published
2026-06-17 04:09 UTCUpdated Record last modified

embedthis goahead UPGRADE

Affected: >= 4.0.0 and <= 4.1.3 · >= 5.0.0 and < 5.1.5

Fixed in: 5.1.5

Safe to downgrade to: a release before 4.0.0

1. Check installed version

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

2. UPGRADE to 5.1.5 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade goahead

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 4.0.0 (Debian / Ubuntu)

apt-cache madison goahead sudo apt install goahead=<VERSION_BEFORE_4.0.0> sudo apt-mark hold goahead

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

dnf --showduplicates list goahead sudo dnf downgrade goahead-<VERSION_BEFORE_4.0.0> sudo dnf versionlock add goahead

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-2021-42342?

goahead: upgrade to 5.1.5. Exact commands for each OS are on this page.

Is CVE-2021-42342 being exploited?

CVE-2021-42342 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-2021-42342 affect?

CVE-2021-42342 affects goahead. Severity is critical (CVSS 9.8). An issue was discovered in GoAhead 4.x and 5.x before 5.1.5. In the file upload filter, user form variables can be passed to CGI scripts without being prefixed with the CGI prefix. This permits tunneling untrusted environment variables into

How urgent is CVE-2021-42342?

Priority 64/100. Critical severity; EPSS top 1%: very likely to be exploited; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-43298 CRITICAL 9.8 UPGRADE The code that performs password matching when using 'Basic' HTTP authentication does not use a constant-time m
CVE-2021-41615 CRITICAL 9.8 DOWNGRADE websda.c in GoAhead WebServer 2.1.8 has insufficient nonce entropy because the nonce calculation relies on the
CVE-2020-15688 HIGH 8.8 UPGRADE The HTTP Digest Authentication in the GoAhead web server before 5.1.2 does not completely protect against repl

References

← Back to latest CVEs