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Vulnerability record · CVE-2021-22959 · published 15 November 2021

CVE-2021-22959: Llhttp http request smuggling vulnerability

LLlhttp · Llhttp

The parser in accepts requests with a space (SP) right after the header name before the colon. This can lead to HTTP Request Smuggling (HRS) in llhttp < v2.1.4 and < v6.0.6.

6.5 CVSS 3.1 Medium EPSS 3.2% · top 12.5% CWE-444 · HTTP request smuggling
6.5CVSS 3.1 base score, v2 6.4
3.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
6References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

The parser in accepts requests with a space (SP) right after the header name before the colon. This can lead to HTTP Request Smuggling (HRS) in llhttp < v2.1.4 and < v6.0.6.

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

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://hackerone.com/reports/1238709 ExploitIssue TrackingThird Party Advisory
https://www.debian.org/security/2022/dsa-5170 Mailing ListThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory
https://hackerone.com/reports/1238709 ExploitIssue TrackingThird Party Advisory
https://www.debian.org/security/2022/dsa-5170 Mailing ListThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-22959), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.