CVE-2026-61629

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.

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.

Summary

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.

Affected versions

dillmann.com.br/nginx-ignition v2.40.0 and (per code inspection of main) earlier 2.x versions whose api/common/server/i18n.go middleware routes the Accept-Language header through language.ParseAcceptLanguage without imposing its own size or character filter. Verified on:

• the official dillmann/nginx-ignition:latest Docker image at v2.40.0 (E2E below)
• main at commit faef4c99442b329cfa4ee8879bdba41c22866a18 by reading api/common/server/i18n.go (the middleware is unchanged)

Privilege required

Unauthenticated. The middleware is registered on the global gin router that serves both the login page and the unauthenticated /api/health style endpoints. Anyone who can reach the HTTP listener (port 8090 by default) is in scope.

Vulnerable code

api/common/server/i18n.go (blob SHA faef4c99442b329cfa4ee8879bdba41c22866a18):

func i18nMiddleware(commands i18n.Commands) gin.HandlerFunc {
    return func(ginCtx *gin.Context) {
        lang := commands.DefaultLanguage()

        langHeader := ginCtx.GetHeader("Accept-Language")
        tags, _, err := language.ParseAcceptLanguage(langHeader)
        if err == nil && len(tags) > 0 {
            for _, tag := range tags {
                if commands.Supports(tag) {
                    lang = tag
                    break
                }
            }
        }

        //nolint:staticcheck
        updatedCtx := context.WithValue(ginCtx.Request.Context(), i18n.ContextKey, lang)
        ginCtx.Request = ginCtx.Request.WithContext(updatedCtx)
        ginCtx.Set(i18n.ContextKey, lang)
        ginCtx.Next()
    }
}

ginCtx.GetHeader("Accept-Language") is the unfiltered HTTP header. Go's default net/http MaxHeaderBytes is 1 << 20 = 1 MiB and nginx-ignition does not override it, so the parser is allowed to receive up to a megabyte of attacker-controlled data.

CVE-2022-32149 hardened ParseAcceptLanguage by counting - characters and rejecting inputs with more than 1000 of them. The guard does not count _ characters even though the scanner converts _ to - at parse time (golang.org/x/text/internal/language/parse.go). A 1 MiB header full of 9-character _abcdefghi tokens contains zero - characters, passes the guard, and then drives the scanner into the O(N²) gobble path.

How Accept-Language reaches ParseAcceptLanguage

Every HTTP request that hits the nginx-ignition API server passes through i18nMiddleware (registered as a global gin middleware). The middleware sequence is:

1. The request enters i18nMiddleware.
2. ginCtx.GetHeader("Accept-Language") returns the full attacker-supplied header value.
3. language.ParseAcceptLanguage(langHeader) runs unfiltered.

No size or character-class filter is applied between (2) and (3). The middleware runs for every gin handler, including unauthenticated paths like the root URL and /api/health (which…

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.

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.

Summary

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.

Affected versions

dillmann.com.br/nginx-ignition v2.40.0 and (per code inspection of main) earlier 2.x versions whose api/common/server/i18n.go middleware routes the Accept-Language header through language.ParseAcceptLanguage without imposing its own size or character filter. Verified on:

• the official dillmann/nginx-ignition:latest Docker image at v2.40.0 (E2E below)
• main at commit faef4c99442b329cfa4ee8879bdba41c22866a18 by reading api/common/server/i18n.go (the middleware is unchanged)

Privilege required

Unauthenticated. The middleware is registered on the global gin router that serves both the login page and the unauthenticated /api/health style endpoints. Anyone who can reach the HTTP listener (port 8090 by default) is in scope.

Vulnerable code

api/common/server/i18n.go (blob SHA faef4c99442b329cfa4ee8879bdba41c22866a18):

func i18nMiddleware(commands i18n.Commands) gin.HandlerFunc {
    return func(ginCtx *gin.Context) {
        lang := commands.DefaultLanguage()

        langHeader := ginCtx.GetHeader("Accept-Language")
        tags, _, err := language.ParseAcceptLanguage(langHeader)
        if err == nil && len(tags) > 0 {
            for _, tag := range tags {
                if commands.Supports(tag) {
                    lang = tag
                    break
                }
            }
        }

        //nolint:staticcheck
        updatedCtx := context.WithValue(ginCtx.Request.Context(), i18n.ContextKey, lang)
        ginCtx.Request = ginCtx.Request.WithContext(updatedCtx)
        ginCtx.Set(i18n.ContextKey, lang)
        ginCtx.Next()
    }
}

ginCtx.GetHeader("Accept-Language") is the unfiltered HTTP header. Go's default net/http MaxHeaderBytes is 1 << 20 = 1 MiB and nginx-ignition does not override it, so the parser is allowed to receive up to a megabyte of attacker-controlled data.

CVE-2022-32149 hardened ParseAcceptLanguage by counting - characters and rejecting inputs with more than 1000 of them. The guard does not count _ characters even though the scanner converts _ to - at parse time (golang.org/x/text/internal/language/parse.go). A 1 MiB header full of 9-character _abcdefghi tokens contains zero - characters, passes the guard, and then drives the scanner into the O(N²) gobble path.

How Accept-Language reaches ParseAcceptLanguage

Every HTTP request that hits the nginx-ignition API server passes through i18nMiddleware (registered as a global gin middleware). The middleware sequence is:

1. The request enters i18nMiddleware.
2. ginCtx.GetHeader("Accept-Language") returns the full attacker-supplied header value.
3. language.ParseAcceptLanguage(langHeader) runs unfiltered.

No size or character-class filter is applied between (2) and (3). The middleware runs for every gin handler, including unauthenticated paths like the root URL and /api/health (which…

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.

nginx ignition has ParseAcceptLanguage _ separator bypass that enables ~75x CPU amplification via Accept-Language header in i18nMiddleware in github.com/lucasdillmann/nginx-ignition