CVE-2026-49336: microsoft kiota-typescript · Improper Handling of Case Sensitivity
Affects microsoft kiota-typescriptSource CVE Database V5
Public exploit available · CVSS 5.5 Medium : upgrade to 1.0.0-preview.102 as a priority.
Data as of 1 Nov 2026, 22:58 UTC
- EPSS
- 0.7% chance of exploitation in 30 days – higher than 54% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 1.0.0-preview.102
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:PExploitation evidence
Disclosed: evidence found.
CVE published 19 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.
What to do
Upgrade microsoft kiota-typescript to 1.0.0-preview.102.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| microsoftkiota-typescript | Affected
| Fixed in
|
npm@microsoft/kiota-http-fetchlibrarypkg:npm/@microsoft/kiota-http-fetchlibraryOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade to @microsoft/kiota-http-fetchlibrary version 1.0.0-preview.102 or later, where the issue is patched. Until upgraded, be aware that the default middleware does not properly strip sensitive headers on redirects, so consider implementing custom middleware to correctly handle header scrubbing or avoid using affected versions in sensitive environments. Patch status is not explicitly confirmed in the vendor advisory, but the description states version 1.0.0-preview.102 patches the issue.
Description
@microsoft/kiota-http-fetchlibrary provides TypeScript libraries for Kiota-generated API clients. In versions 1.0.0-preview.97 through 1.0.0-preview.101, `@microsoft/kiota-http-fetchlibrary`'s `RedirectHandler` is documented as stripping `Authorization` and `Cookie` from cross-origin redirect targets, but the default `scrubSensitiveHeaders` callback in `RedirectHandlerOptions` uses case-sensitive property deletion (`delete headers.Authorization`, `delete headers.Cookie`) on a headers object that `FetchRequestAdapter.getRequestFromRequestInformation` has already lower-cased. The delete therefore targets keys that do not exist, the scrub is a no-op, and any Bearer token or Cookie attached by a kiota-generated SDK is forwarded to an attacker-controlled host across a 30x redirect. This is reachable in the default middleware chain (`MiddlewareFactory.getDefaultMiddlewares`) with no custom configuration, and applies to every kiota-generated TypeScript SDK that uses `BaseBearerTokenAuthenticationProvider` or any other authentication provider that sets the `Authorization` request header. Version 1.0.0-preview.102 patches the issue.