CVE-2023-37276 | aiohttp vulnerable to HTTP request smuggling

Exp

aiohttp is an asynchronous HTTP client/server framework for asyncio and Python. aiohttp v3.8.4 and earlier are bundled with llhttp v6.0.6. Vulnerable code is used by aiohttp for its HTTP request parser when available which is the default case when installing from a wheel. This vulnerability only affects users of aiohttp as an HTTP server (ie `aiohttp.Application`), you are not affected by this vulnerability if you are using aiohttp as an HTTP client library (ie `aiohttp.ClientSession`). Sending a crafted HTTP request will cause the server to misinterpret one of the HTTP header values leading to HTTP request smuggling. This issue has been addressed in version 3.8.5. Users are advised to upgrade. Users unable to upgrade can reinstall aiohttp using `AIOHTTP_NO_EXTENSIONS=1` as an environment variable to disable the llhttp HTTP request parser implementation. The pure Python implementation isn't vulnerable.

Published: 2023-07-19 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-37276 is rated High Exploit Risk (68.4/100): CVSS Medium severity, with high exploitation likelihood (EPSS 6.13%, 91th percentile). 2 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-2023-37276

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

Exploit prediction scoring system (EPSS) score for CVE-2023-37276

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 2026-05-15 5.78% 6.13% +0.36%
2 2025-11-21 1.50% 5.78% +4.27%
3 2025-11-18 — 1.50% —

Full EPSS history (16 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-37276

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
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]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2023-37276

GitHub Security Advisory for CVE-2023-37276

GHSA-45c4-8wx5-qw6w · Severity: medium · Ecosystem: pip — aiohttp.web.Application vulnerable to HTTP request smuggling via llhttp HTTP request parser

OS Trackers for CVE-2023-37276

vendor priority summary link
debian unimportant CVE-2023-37276 unimportant priority: Debian including 1 source packages (python-aiohttp), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2023-37276
redhat medium — https://access.redhat.com/security/cve/CVE-2023-37276
suse medium CVE-2023-37276 severity moderate: SUSE including 4 source package names (python-aiohttp, python-aiohttp-doc, python3-aiohttp, python311-aiohttp), 17 product×package rows across 7 product lines (SUSE Linux Enterprise Module for Public Cloud 15 SP1, SUSE Linux Enterprise Module for Public Cloud 15 SP2, … (7 product lines)): Known Not Affected 17. https://www.suse.com/security/cve/CVE-2023-37276/
ubuntu medium CVE-2023-37276 medium priority: Ubuntu including 1 source packages (python-aiohttp), 12 status rows across 12 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): not-affected 6, ignored 5, released 1. https://ubuntu.com/security/CVE-2023-37276

Affected software / configurations for CVE-2023-37276

Vendor Product Version Raw CPE
aiohttp aiohttp <= 3.8.4 cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*

References for CVE-2023-37276

cvelogic Threat Intelligence