How severe is CVE-2023-35944?

CVE-2023-35944 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.

Is CVE-2023-35944 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-35944?

CVE-2023-35944 affects Envoyproxy Envoy. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2023-35944?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2023-35944 published?

CVE-2023-35944 was published on 2023-07-25 and last updated on 2026-06-17.

CVE-2023-35944

CVE-2023-35944 is a high-severity vulnerability in Envoyproxy Envoy with a CVSS 3.x base score of 8.2. 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: High (CVSS 3.x base score 8.2)
EPSS exploit prediction: 1% (44th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Envoyproxy Envoy
Published: 2023-07-25
Last modified: 2026-06-17

Description

Envoy is an open source edge and service proxy designed for cloud-native applications. Envoy allows mixed-case schemes in HTTP/2, however, some internal scheme checks are case-sensitive. Prior to versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, this can lead to the rejection of requests with mixed-case schemes such as `htTp` or `htTps`, or the bypassing of some requests such as `https` in unencrypted connections. With a fix in versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, Envoy will now lowercase scheme values by default, and change the internal scheme checks that were case-sensitive to be case-insensitive. There are no known workarounds for this issue.

Frequently asked questions

What is CVE-2023-35944?: Envoy is an open source edge and service proxy designed for cloud-native applications. Envoy allows mixed-case schemes in HTTP/2, however, some internal scheme checks are case-sensitive. Prior to versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, this can lead to the rejection of requests with mixed-case schemes such as `htTp` or `htTps`, or the bypassing of some requests such as `https` in unencrypted connections. With a fix in versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, Envoy will now lowercase scheme values by default, and change the internal scheme checks that were case-sensitive to be case-insensitive. There are no known workarounds for this issue.
How severe is CVE-2023-35944?: CVE-2023-35944 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.
Is CVE-2023-35944 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (44th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-35944?: CVE-2023-35944 affects Envoyproxy Envoy. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2023-35944?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-35944 published?: CVE-2023-35944 was published on 2023-07-25 and last updated on 2026-06-17.

References

https://github.com/envoyproxy/envoy/security/advisories/GHSA-pvgm-7jpg-pw5g

Affected products (1)

cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*

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