CVE-2021-32715 | Lenient Parsing of Content-Length Header When Prefixed with Plus Sign

Exp

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.

Published: 2021-07-07 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-32715 is rated Exploit Available (50/100): CVSS Low severity, with medium exploitation likelihood (EPSS 0.29%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-32715

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-32715

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.21% 0.29% +0.08%
2 2025-11-18 0.29% 0.21% -0.08%
3 2025-03-30 — 0.29% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-32715

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
3.1 3.1 LOW
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 1.6 1.4 [email protected]
5.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 1.4 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-32715

GitHub Security Advisory for CVE-2021-32715

GHSA-f3pg-qwvg-p99c · Severity: low · Ecosystem: rust — Lenient Parsing of Content-Length Header When Prefixed with Plus Sign

OS Trackers for CVE-2021-32715

vendor priority summary link
debian not yet assigned CVE-2021-32715 not yet assigned priority: Debian including 1 source packages (rust-hyper), 4 status rows across 4 suites (bookworm, forky, sid, trixie): resolved 4. https://security-tracker.debian.org/tracker/CVE-2021-32715
suse low CVE-2021-32715 severity low: SUSE including 48 source package names (afterburn-5.0.0-6.1, afterburn-5.2.0-150300.1.3, …), 153 product×package rows across 30 product lines (SUSE CaaS Platform 4.0, SUSE Enterprise Storage 6, … (30 product lines)): Known Not Affected 137, Fixed 16. https://www.suse.com/security/cve/CVE-2021-32715/
ubuntu medium CVE-2021-32715 medium priority: Ubuntu including 1 source packages (rust-hyper), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 6, DNE 4, ignored 4, needed 1, released 1. https://ubuntu.com/security/CVE-2021-32715

Affected software / configurations for CVE-2021-32715

Vendor Product Version Raw CPE
hyper hyper < 0.14.10 cpe:2.3:a:hyper:hyper:*:*:*:*:*:rust:*:*

References for CVE-2021-32715

cvelogic Threat Intelligence