Bug 2539016 (CVE-2026-61629)

Summary: CVE-2026-61629 github.com/lucasdillmann/nginx-ignition: golang.org/x/text: nginx-ignition: Denial of Service via Accept-Language header processing
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerability-draftAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in nginx-ignition. The gin i18n middleware in nginx-ignition's API server processes the Accept-Language header using golang.org/x/text/language.ParseAcceptLanguage. This parser exhibits quadratic-time behavior when handling long lists of malformed language tags, specifically when using underscore (_) characters, which are not subject to the same length caps as hyphen (-) characters. A remote, unauthenticated attacker can send a crafted Accept-Language header, leading to significant CPU amplification and causing a Denial of Service (DoS) on the affected server.
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Description OSIDB Bzimport 2026-09-22 21:58:25 UTC 
nginx ignition is a user interface for the nginx web server. In versions 2.29.0 through 2.40.0, the gin i18n middleware in nginx-ignition's API server runs in front of every HTTP request and calls `golang.org/x/text/language.ParseAcceptLanguage` on the raw `Accept-Language` header without imposing any size or shape filter. The underlying parser has quadratic-time behaviour on long lists of malformed language tags. The CVE-2022-32149 guard that golang.org/x/text added in v0.3.8 caps the number of `-` characters in the input at 1000, but it does not cap `_` characters even though the parser's internal scanner aliases `_` to `-` before parsing. A single unauthenticated GET request with an `Accept-Language` header built out of `_` separators burns about 2.4 seconds of server CPU on the host running nginx-ignition; ten concurrent attackers saturate a ten-core box for the duration of the attack while consuming ~10 MiB/s of upstream bandwidth. Version 2.40.1 fixes this issue.