CVE-2021-26843: An issue was discovered in sthttpd through 2.27.1

Q: How do I fix CVE-2021-26843?

sthttpd: upgrade to newer than 2.27.1. Exact commands for each OS are on this page.

Q: Is CVE-2021-26843 being exploited?

CVE-2021-26843 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-26843 affect?

CVE-2021-26843 affects sthttpd. Severity is high (CVSS 7.5). An issue was discovered in sthttpd through 2.27.1. On systems where the strcpy function is implemented with memcpy, the de_dotdot function may cause a Denial-of-Service (daemon crash) due to overlapping memory ranges being passed to memcpy.

Q: How urgent is CVE-2021-26843?

Priority 55/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADE

CVE-2021-26843 is a high-severity flaw (CVSS 7.5) affecting sthttpd. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in sthttpd through 2.27.1. On systems where the strcpy function is implemented with memcpy, the de_dotdot function may cause a Denial-of-Service (daemon crash) due to overlapping memory ranges being passed to memcpy. This can triggered with an HTTP GET request for a crafted filename. NOTE: this is similar to CVE-2017-10671, but occurs in a different part of the de_dotdot function.

Why this priority

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

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 27%)
CISA exploited list	No
Weakness	CWE-119
Published	2021-02-07
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: sthttpd project

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

Am I affected?

Timeline

2021-02-07 21:15 UTCPublished CVE record published
2026-06-17 03:43 UTCUpdated Record last modified

sthttpd project sthttpd UPGRADE

Affected: <= 2.27.1

Fixed in: newer than 2.27.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 2.27.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sthttpd

Note

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

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-2021-26843?

sthttpd: upgrade to newer than 2.27.1. Exact commands for each OS are on this page.

Is CVE-2021-26843 being exploited?

CVE-2021-26843 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-2021-26843 affect?

CVE-2021-26843 affects sthttpd. Severity is high (CVSS 7.5). An issue was discovered in sthttpd through 2.27.1. On systems where the strcpy function is implemented with memcpy, the de_dotdot function may cause a Denial-of-Service (daemon crash) due to overlapping memory ranges being passed to memcpy.

How urgent is CVE-2021-26843?

Priority 55/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2017-10671 HIGH 7.8 UPGRADE Heap-based Buffer Overflow in the de_dotdot function in libhttpd.c in sthttpd before 2.27.1 allows remote atta
CVE-2013-0348 LOW 2.1 UPGRADE MITIGATE thttpd.c in sthttpd before 2.26.4-r2 and thttpd 2.25b use world-readable permissions for /var/log/thttpd.log,

References

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