How severe is CVE-2021-22959?

CVE-2021-22959 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-22959 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-22959?

CVE-2021-22959 primarily affects Llhttp. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-22959?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-22959 published?

CVE-2021-22959 was published on 2021-11-15 and last updated on 2026-06-17.

CVE-2021-22959

CVE-2021-22959 is a medium-severity vulnerability in Llhttp with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-444.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 6.4
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Llhttp
Published: 2021-11-15
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-22959?: 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.
How severe is CVE-2021-22959?: CVE-2021-22959 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-22959 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-22959?: CVE-2021-22959 primarily affects Llhttp. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-22959?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-22959 published?: CVE-2021-22959 was published on 2021-11-15 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:llhttp:llhttp:*:*:*:*:*:node.js:*:*
cpe:2.3:a:oracle:graalvm:20.3.4:*:*:*:enterprise:*:*:*
cpe:2.3:a:oracle:graalvm:21.3.0:*:*:*:enterprise:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

More vulnerabilities in Llhttp

CVE-2022-35256 — Medium (CVSS 6.5): The llhttp parser in the http module in Node v18.7.0 does not correctly handle header fields that are not terminated…
CVE-2022-32215 — Medium (CVSS 6.5): The llhttp parser <v14.20.1, <v16.17.1 and <v18.9.1 in the http module in Node.js does not correctly handle multi-line…
CVE-2022-32214 — Medium (CVSS 6.5): The llhttp parser <v14.20.1, <v16.17.1 and <v18.9.1 in the http module in Node.js does not strictly use the CRLF…
CVE-2022-32213 — Medium (CVSS 6.5): The llhttp parser <v14.20.1, <v16.17.1 and <v18.9.1 in the http module in Node.js does not correctly parse and validate…
CVE-2021-22960 — Medium (CVSS 6.5): The parse function in llhttp < 2.1.4 and < 6.0.6. ignores chunk extensions when parsing the body of chunked requests.…

All CVEs affecting Llhttp →

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