How severe is CVE-2021-32715?

CVE-2021-32715 has a CVSS 3.x base score of 3.1, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2021-32715 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-32715?

CVE-2021-32715 affects Hyper. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-32715?

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

When was CVE-2021-32715 published?

CVE-2021-32715 was published on 2021-07-07 and last updated on 2026-06-17.

CVE-2021-32715

CVE-2021-32715 is a low-severity vulnerability in Hyper with a CVSS 3.x base score of 3.1. 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: Low (CVSS 3.x base score 3.1)
CVSS v2: 4.3
EPSS exploit prediction: 1% (55th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Hyper
Published: 2021-07-07
Last modified: 2026-06-17

Description

hyper is an HTTP library for rust. hyper's HTTP/1 server code had a flaw that incorrectly parses and accepts requests with a `Content-Length` header with a prefixed plus sign, when it should have been rejected as illegal. This combined with an upstream HTTP proxy that doesn't parse such `Content-Length` headers, but forwards them, can result in "request smuggling" or "desync attacks". The flaw exists in all prior versions of hyper prior to 0.14.10, if built with `rustc` v1.5.0 or newer. The vulnerability is patched in hyper version 0.14.10. Two workarounds exist: One may reject requests manually that contain a plus sign prefix in the `Content-Length` header or ensure any upstream proxy handles `Content-Length` headers with a plus sign prefix.

Frequently asked questions

What is CVE-2021-32715?: hyper is an HTTP library for rust. hyper's HTTP/1 server code had a flaw that incorrectly parses and accepts requests with a `Content-Length` header with a prefixed plus sign, when it should have been rejected as illegal. This combined with an upstream HTTP proxy that doesn't parse such `Content-Length` headers, but forwards them, can result in "request smuggling" or "desync attacks". The flaw exists in all prior versions of hyper prior to 0.14.10, if built with `rustc` v1.5.0 or newer. The vulnerability is patched in hyper version 0.14.10. Two workarounds exist: One may reject requests manually that contain a plus sign prefix in the `Content-Length` header or ensure any upstream proxy handles `Content-Length` headers with a plus sign prefix.
How severe is CVE-2021-32715?: CVE-2021-32715 has a CVSS 3.x base score of 3.1, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2021-32715 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-32715?: CVE-2021-32715 affects Hyper. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-32715?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-32715 published?: CVE-2021-32715 was published on 2021-07-07 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:hyper:hyper:*:*:*:*:*:rust:*:*

More vulnerabilities in Hyper

CVE-2020-35863 — Critical (CVSS 9.8): An issue was discovered in the hyper crate before 0.12.34 for Rust. HTTP request smuggling can occur. Remote code…
CVE-2023-26964 — High (CVSS 7.5): An issue was discovered in hyper v0.13.7. h2-0.2.4 Stream stacking occurs when the H2 component processes HTTP2…
CVE-2022-31394 — High (CVSS 7.5): Hyperium Hyper before 0.14.19 does not allow for customization of the max_header_list_size method in the H2 third-party…
CVE-2021-32714 — Medium (CVSS 5.9): hyper is an HTTP library for Rust. In versions prior to 0.14.10, hyper's HTTP server and client code had a flaw that…
CVE-2017-18587 — Medium (CVSS 5.3): An issue was discovered in the hyper crate before 0.9.18 for Rust. It mishandles newlines in headers.
CVE-2021-21299 — Medium (CVSS 4.8): hyper is an open-source HTTP library for Rust (crates.io). In hyper from version 0.12.0 and before versions 0.13.10 and…

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