CVE-2023-35944
Envoy allows mixed-case schemes in HTTP/2, however, some internal scheme checks are case-sensitive.
Does this matter?
Lower severity and a low EPSS score (0.70%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- EPSS
- 0.70% probability · 53th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-20, CWE-444
- Affected
- envoyproxy/envoy
- Source
- security-advisories@github.com
EPSS 0.7% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-pvgm-7jpg-pw5gExploit, Third Party Advisory
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-pvgm-7jpg-pw5gExploit, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.