CVE-2021-40540

Name: CVE-2021-40540
Creator: NVD / NIST
Published: 2021-09-07T02:15:07.13+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 2.54%

Last modified Jun 17, 2026

CVE-2021-40540 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. ulfius_uri_logger in Ulfius HTTP Framework before 2.7.4 omits con_info initialization and a con_info->request NULL check for certain malformed HTTP requests.. EPSS estimates a 2.54% chance of exploitation in the next 30 days.

Description

ulfius_uri_logger in Ulfius HTTP Framework before 2.7.4 omits con_info initialization and a con_info->request NULL check for certain malformed HTTP requests.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

2.54%

83.0th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Ulfius Project	Ulfius	< 2.7.4

References

http://packetstormsecurity.com/files/164152/Ulfius-Web-Framework-Remote-Memory-Corruption.htmlExploit, Third Party Advisory, VDB Entry
https://github.com/babelouest/ulfius/commit/c83f564c184a27145e07c274b305cabe943bbfaaPatch, Third Party Advisory
https://github.com/babelouest/ulfius/compare/v2.7.3...v2.7.4Patch, Third Party Advisory
http://packetstormsecurity.com/files/164152/Ulfius-Web-Framework-Remote-Memory-Corruption.htmlExploit, Third Party Advisory, VDB Entry
https://github.com/babelouest/ulfius/commit/c83f564c184a27145e07c274b305cabe943bbfaaPatch, Third Party Advisory
https://github.com/babelouest/ulfius/compare/v2.7.3...v2.7.4Patch, Third Party Advisory

Timeline

Published: Sep 7, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-40540?

ulfius_uri_logger in Ulfius HTTP Framework before 2.7.4 omits con_info initialization and a con_info->request NULL check for certain malformed HTTP requests.

How severe is CVE-2021-40540?

CVE-2021-40540 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.54% probability of exploitation in the next 30 days.

How do I fix CVE-2021-40540?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-40540?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST