How severe is CVE-2021-33197?

CVE-2021-33197 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2021-33197 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33197?

CVE-2021-33197 affects Golang Go. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-33197?

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

When was CVE-2021-33197 published?

CVE-2021-33197 was published on 2021-08-02 and last updated on 2026-06-17.

CVE-2021-33197

CVE-2021-33197 is a medium-severity vulnerability in Golang Go with a CVSS 3.x base score of 5.3. 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-862.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 4.3
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-862
Affected product: Golang Go
Published: 2021-08-02
Last modified: 2026-06-17

Description

In Go before 1.15.13 and 1.16.x before 1.16.5, some configurations of ReverseProxy (from net/http/httputil) result in a situation where an attacker is able to drop arbitrary headers.

Frequently asked questions

What is CVE-2021-33197?: In Go before 1.15.13 and 1.16.x before 1.16.5, some configurations of ReverseProxy (from net/http/httputil) result in a situation where an attacker is able to drop arbitrary headers.
How severe is CVE-2021-33197?: CVE-2021-33197 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2021-33197 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33197?: CVE-2021-33197 affects Golang Go. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-33197?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-33197 published?: CVE-2021-33197 was published on 2021-08-02 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*

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