azureauthextension Authenticate method does not validate bearer tokens, allowing auth bypass via replay

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What is CVE-2026-42602?

CVE-2026-42602 is a vulnerability classified as Observable Timing Discrepancy, Improper Authentication, Authentication Bypass by Spoofing, and 2 more types, affecting opentelemetry-collector-contrib (affected versions: >= 0.124.0, <= 0.150.0). This vulnerability is rated High, with a CVSS score of 8.1. Public exploit code or evidence is available for this vulnerability, but that does not confirm exploitation in the wild.

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Overview

Original source data

azureauthextension is the Azure Authenticator Extension. From 0.124.0 to 0.150.0, a server-side authentication bypass in azureauthextension allows any party who holds a single valid Azure access token for any scope the collector's configured identity can mint for to authenticate to any OpenTelemetry receiver that uses auth: azure_auth. The extension's Authenticate method does not validate incoming bearer tokens as JWTs. Instead, it calls its own configured credential to obtain an access token and compares the client's token to the result with string equality — and the scope for that server-side token request is taken from the client-supplied Host header. As a result, a token minted for any Azure resource the service principal has ever been issued a token for (ARM, Graph, Key Vault, Storage, etc.) will authenticate to the collector if the attacker picks a matching Host. Tokens are replayable for the full issued lifetime (commonly several hours for managed identity tokens).

Affected products and scope

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Technical details

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Exploitability

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Technical impact

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Business impact

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Remediation

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Detection

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