CVE-2026-40490

Description

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. When redirect following is enabled (followRedirect(true)), versions of AsyncHttpClient prior to 3.0.9 and 2.14.5 forward Authorization and Proxy-Authorization headers along with Realm credentials to arbitrary redirect targets regardless of domain, scheme, or port changes. This leaks credentials on cross-domain redirects and HTTPS-to-HTTP downgrades. Additionally, even when stripAuthorizationOnRedirect is set to true, the Realm object containing plaintext credentials is still propagated to the redirect request, causing credential re-generation for Basic and Digest authentication schemes via NettyRequestFactory. An attacker who controls a redirect target (via open redirect, DNS rebinding, or MITM on HTTP) can capture Bearer tokens, Basic auth credentials, or any other Authorization header value. The fix in versions 3.0.9 and 2.14.5 automatically strips Authorization and Proxy-Authorization headers and clears Realm credentials whenever a redirect crosses origin boundaries (different scheme, host, or port) or downgrades from HTTPS to HTTP. For users unable to upgrade, set `(stripAuthorizationOnRedirect(true))` in the client config and avoid using Realm-based authentication with redirect following enabled. Note that `(stripAuthorizationOnRedirect(true))` alone is insufficient on versions prior to 3.0.9 and 2.14.5 because the Realm bypass still re-generates credentials. Alternatively, disable redirect following (`followRedirect(false)`) and handle redirects manually with origin validation.

CVSS v3.1 Score

6.8

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0007

Probability of exploitation

0.20%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-200 CWE-200

References

Other References

https://github.com/AsyncHttpClient/async-http-client/commit/6b2fbb7f8 https://github.com/AsyncHttpClient/async-http-client/commit/ae557ad35246721c09dafb2976609cd0004e78ae https://github.com/AsyncHttpClient/async-http-client/releases/tag/async-http-client-project-2.14.5 https://github.com/AsyncHttpClient/async-http-client/releases/tag/async-http-client-project-3.0.9 https://github.com/AsyncHttpClient/async-http-client/security/advisories/GHSA-cmxv-58fp-fm3g

Frequently Asked Questions

What is CVE-2026-40490? +

The AsyncHttpClient (AHC) library allows Java applications to easily execute HTTP requests and asynchronously process HTTP responses. When redirect following is enabled (followRedirect(true)), versions of AsyncHttpClient prior to 3.0.9 and 2.14.5 forward Authorization and Proxy-Authorization headers along with Realm credentials to arbitrary redirect targets regardless of domain, scheme, or port changes. This leaks credentials on cross-domain redirects and HTTPS-to-HTTP downgrades. Additionally, even when stripAuthorizationOnRedirect is set to true, the Realm object containing plaintext credentials is still propagated to the redirect request, causing credential re-generation for Basic and Digest authentication schemes via NettyRequestFactory. An attacker who controls a redirect target (via open redirect, DNS rebinding, or MITM on HTTP) can capture Bearer tokens, Basic auth credentials, or any other Authorization header value. The fix in versions 3.0.9 and 2.14.5 automatically strips Authorization and Proxy-Authorization headers and clears Realm credentials whenever a redirect crosses origin boundaries (different scheme, host, or port) or downgrades from HTTPS to HTTP. For users unable to upgrade, set `(stripAuthorizationOnRedirect(true))` in the client config and avoid using Realm-based authentication with redirect following enabled. Note that `(stripAuthorizationOnRedirect(true))` alone is insufficient on versions prior to 3.0.9 and 2.14.5 because the Realm bypass still re-generates credentials. Alternatively, disable redirect following (`followRedirect(false)`) and handle redirects manually with origin validation. It has a CVSS v3.1 base score of 6.8 (MEDIUM).

How severe is CVE-2026-40490? +

CVE-2026-40490 has a CVSS v3.1 score of 6.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0007, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-40490? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2025-15625

Unauthenticated user is able to execute arbitrary SQL commands in Sparx Pro Cloud Server database in certain cases.

CVE-2026-22051

StorageGRID (formerly StorageGRID Webscale) versions prior to 11.9.0.13 and 12.0.0.6 are susceptible to a Information Disclosure vulnerability. Successful exploit could …

CVE-2026-40166

authentik is an open-source identity provider. In versions prior to 2025.12.5 and 2026.2.0-rc1 through 2026.2.2, authenticated non-admin users with at …

CVE-2025-22138

@codidact/qpixel is a Q&A-based community knowledge-sharing software. In affected versions when a category is set to private or limited-visibility within …

CVE-2025-0659

A path traversal vulnerability exists in the Rockwell Automation DataEdge Platform DataMosaix Private Cloud. By specifying the character sequence in …

CVE-2025-24884

kube-audit-rest is a simple logger of mutation/creation requests to the k8s api. If the "full-elastic-stack" example vector configuration was used …