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CVE-2025-12977 is an improper input validation vulnerability in Fluent Bit affecting the in_http, in_splunk, and in_elasticsearch input plugins. When Fluent Bit is configured to derive record tags from user-controlled fields via the tag_key option, the resulting tag values bypass normal sanitization. An attacker with network access to the HTTP input, or the ability to write records into Splunk or Elasticsearch feeding Fluent Bit, can supply tag_key values containing special characters such as newlines, control characters, or path traversal sequences like ../. Because Fluent Bit tags are used for routing and some downstream outputs derive filenames or content from tags, maliciously crafted tags can be accepted as valid and propagated through the pipeline, enabling downstream injection and routing abuse.
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A partial string comparison flaw in Fluent Bit’s tag_key handling that can let an attacker manipulate routing tags (and thus log routing/processing) when they can send records to affected inputs.
A critical input validation vulnerability in Fluent Bit's in_http, in_splunk, and in_elasticsearch input plugins allows attackers to inject special characters into tag_key values, leading to newline injection, path traversal, forged record injection, or log misrouting. This impacts data integrity and log routing in environments using Fluent Bit for log collection and processing.
An improper input validation issue in Fluent Bit tag handling that allows injection of newlines/traversal/control characters via user-controlled fields, potentially corrupting downstream logs and enabling log manipulation.
Improper input validation: tags derived from user-controlled record fields via Tag_Key bypass sanitization, enabling control characters/newlines/path traversal sequences that can corrupt outputs and enable downstream injection or filesystem write abuse depending on outputs.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.