CVE-2001-1496: Off-by-one buffer overflow in Basic Authentication in Acme Labs thttpd 1.95 through 2.20 allows remote attacke

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CRITICAL 9.8REMOTEUPGRADE

CVE-2001-1496 is a critical-severity flaw (CVSS 9.8) affecting thttpd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Off-by-one buffer overflow in Basic Authentication in Acme Labs thttpd 1.95 through 2.20 allows remote attackers to cause a denial of service and possibly execute arbitrary code.

Why this priority

Critical severity
EPSS top 8%: 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	5.1% (top 8%)
CISA exploited list	No
Weakness	CWE-193
Published	2001-12-31
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: acme

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2001-12-31 05:00 UTCPublished CVE record published
2026-06-16 21:56 UTCUpdated Record last modified

acme thttpd UPGRADE

Affected: >= 1.95 and <= 2.20

Fixed in: newer than 2.20

Safe to downgrade to: a release before 1.95

1. Check installed version

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

2. UPGRADE to newer than 2.20 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade thttpd

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 1.95 (Debian / Ubuntu)

apt-cache madison thttpd sudo apt install thttpd=<VERSION_BEFORE_1.95> sudo apt-mark hold thttpd

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

dnf --showduplicates list thttpd sudo dnf downgrade thttpd-<VERSION_BEFORE_1.95> sudo dnf versionlock add thttpd

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-2001-1496?

thttpd: upgrade to newer than 2.20. Exact commands for each OS are on this page.

Is CVE-2001-1496 being exploited?

CVE-2001-1496 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-2001-1496 affect?

CVE-2001-1496 affects thttpd. Severity is critical (CVSS 9.8). Off-by-one buffer overflow in Basic Authentication in Acme Labs thttpd 1.95 through 2.20 allows remote attackers to cause a denial of service and possibly execute arbitrary code.

How urgent is CVE-2001-1496?

Priority 62/100. Critical severity; EPSS top 8%: very likely to be exploited; Remotely exploitable, no login, no user action

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References

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