CVE-2020-26281: Async h1 Async-h1 Request Smuggling Possible With Vulnerability

MODERATE
Advisory Identifier: GHSA-4vr9-8cjf-vf9c
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CVSS 6.8
CWE-444
Published
Advisory Summary

CVE-2020-26281 is a MODERATE (CVSS 6.8) async-h1 request smuggling possible with vulnerability (CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')) affecting Async h1 libraries in the crates.io ecosystem. The issue involves async-h1 request smuggling possible with long unread bodies. Remediation is available by upgrading affected packages to version 2.3.0.

CVE-2020-26281 at a Glance

CVE Identifier CVE-2020-26281
GHSA Identifier GHSA-4vr9-8cjf-vf9c
Severity MODERATE
CVSS v3.1 Base Score 6.8
CWE Classification CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Affected Product Async h1
Package Ecosystem crates.io
Published Date
Last Updated

Security Impact

CVSS: 6.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2020-26281

To remediate this vulnerability, upgrade all affected Async h1 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

async-h1 fixed: 2.3.0 
Upgrade async-h1 to 2.3.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for async-h1

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-26281, inspect your project dependencies for Async h1:

inspect dependencies for async-h1

Analyze the terminal output to locate any version of Async h1 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.3.0), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'), where the product acts as an intermediary http agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed http requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. In Async h1, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact This vulnerability affects any webserver that uses async-h1 behind a reverse proxy, including all such Tide applications. If the server does not read the body of a request which is longer than some buffer length, async-h1 will attempt to read a subsequent request from the body content starting at that offset into the body. One way to exploit this vulnerability would be for an adversary to craft a request such that the body contains a request that would not be noticed by a reverse proxy, allowing it to forge forwarded/x-forwarded headers. If an application trusted the authenticity of these headers, it could be misled by the smuggled request. Another potential concern with this vulnerability is that if a reverse proxy is sending multiple http clients' requests along the same keep-alive connection, it would be possible for the smuggled request to specify a long content and capture another user's request in its body. This content could be captured in a post request to an endpoint that allows the content to be subsequently retrieved by the adversary. ### Patches This has been addressed in async-h1 2.3.0 and previous versions have been yanked. ### Workarounds none ### References https://github.com/http-rs/async-h1/releases/tag/v2.3.0 ### For more information If you have any questions or comments about this advisory: * Open an issue in [async-h1](https://github.com/http-rs/async-h1) * Contact a core team member on [zulip](https://http-rs.zulip-chat.com) or [discord](https://discord.gg/x2gKzst)

CVE-2020-26281 Affected Async h1 Versions

1 component(s)
Fixed Versions:
2.3.0
Product / Package Ecosystem Affected Versions Fixed Version
async-h1
 crates.io
< 2.3.0
2.3.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/http-rs/async-h1/security/advisories/GHSA-4vr9-8cjf-vf9c
NVD — CVE-2020-26281 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-26281
Async h1 Source Repository REPOSITORY
https://github.com/http-rs/async-h1
Async h1 Release RELEASE
https://github.com/http-rs/async-h1/releases/tag/v2.3.0
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2020-0093.html

Frequently Asked Questions

What is CVE-2020-26281?
CVE-2020-26281 is a security vulnerability in Async h1 involving Async-h1 request smuggling possible with long unread bodies under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling').
Which Async h1 versions are affected?
Affected versions include releases prior to 2.3.0 across affected packages: async-h1.
What version fixes CVE-2020-26281?
Upgrading to 2.3.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is async-h1 affected?
Yes, async-h1 is affected in releases prior to 2.3.0. Upgrade your dependency to 2.3.0 or later.
What is the CVSS score of CVE-2020-26281?
CVE-2020-26281 has a CVSS v3.1 base score of 6.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N.
What CWE is associated with CVE-2020-26281?
CVE-2020-26281 is classified under CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') (The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.).
How can I check crates.io dependencies for CVE-2020-26281?
Run the dependency tree command: 'inspect dependencies for async-h1'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4vr9-8cjf-vf9c",
  "modified" : "2021-10-08T22:14:28Z",
  "published" : "2021-10-12T16:00:37Z",
  "aliases" : [ "CVE-2020-26281" ],
  "summary" : "Async-h1 request smuggling possible with long unread bodies",
  "details" : "### Impact\nThis vulnerability affects any webserver that uses async-h1 behind a reverse proxy, including all such Tide applications.\n\nIf the server does not read the body of a request which is longer than some buffer length, async-h1 will attempt to read a subsequent request from the body content starting at that offset into the body.\n\nOne way to exploit this vulnerability would be for an adversary to craft a request such that the body contains a request that would not be noticed by a reverse proxy, allowing it to forge forwarded/x-forwarded headers. If an application trusted the authenticity of these headers, it could be misled by the smuggled request.\n\nAnother potential concern with this vulnerability is that if a reverse proxy is sending multiple http clients' requests along the same keep-alive connection, it would be possible for the smuggled request to specify a long content and capture another user's request in its body. This content could be captured in a post request to an endpoint that allows the content to be subsequently retrieved by the adversary.\n\n\n### Patches\nThis has been addressed in async-h1 2.3.0 and previous versions have been yanked.\n\n### Workarounds\nnone\n\n### References\nhttps://github.com/http-rs/async-h1/releases/tag/v2.3.0\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [async-h1](https://github.com/http-rs/async-h1)\n* Contact a core team member on [zulip](https://http-rs.zulip-chat.com) or [discord](https://discord.gg/x2gKzst)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "async-h1"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.3.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/http-rs/async-h1/security/advisories/GHSA-4vr9-8cjf-vf9c"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-26281"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/http-rs/async-h1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/http-rs/async-h1/releases/tag/v2.3.0"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2020-0093.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-444" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-10-08T22:14:28Z",
    "nvd_published_at" : "2020-12-21T22:15:00Z"
  }
}