CVE-2026-84243

The GNU C Library project provides the core libraries for the GNU system and GNU/Linux systems, as well as many other systems that use Linux as the kernel. These libraries provide critical APIs including ISO C11, POSIX.1-2008, BSD, OS-specific APIs and more. These APIs include such foundational facilities as open, read, write, malloc, printf, getaddrinfo, dlopen, pthread_create, crypt, login, exit and more.

Security Fix(es):

The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this.

The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE.

LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.(CVE-2026-84243)

The GNU C Library project provides the core libraries for the GNU system and GNU/Linux systems, as well as many other systems that use Linux as the kernel. These libraries provide critical APIs including ISO C11, POSIX.1-2008, BSD, OS-specific APIs and more. These APIs include such foundational facilities as open, read, write, malloc, printf, getaddrinfo, dlopen, pthread_create, crypt, login, exit and more.

Security Fix(es):

The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this.

The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE.

LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.(CVE-2026-84243)

The GNU C Library project provides the core libraries for the GNU system and GNU/Linux systems, as well as many other systems that use Linux as the kernel. These libraries provide critical APIs including ISO C11, POSIX.1-2008, BSD, OS-specific APIs and more. These APIs include such foundational facilities as open, read, write, malloc, printf, getaddrinfo, dlopen, pthread_create, crypt, login, exit and more.

Security Fix(es):

The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this.

The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE.

LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.(CVE-2026-84243)

The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this. The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE. LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.

The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this.

The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE.

LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.

The gettext family of functions in the GNU C Library version 2.0 and later accept LANGUAGE environment variable entries that contain '/' or that are equal to "..", unless the program is setuid or setgid (AT_SECURE). An attacker who can set LANGUAGE in the environment of a program that uses gettext can make it load a message catalog (.mo file) from an arbitrary location in the file system. A crafted .mo file can crash the program through out-of-range offsets, or supply translations whose format directives do not match the arguments passed by the program. That causes undefined behaviour in the printf family of functions and may allow arbitrary code execution with the privileges of the program. The safety of message catalogs relies on them being installed in trusted, read-only locations, and the directory traversal bypasses this.

The fix for CVE-2014-0475 rejects ".." path components in locale names passed to setlocale or taken from the LC_ALL, LC_* and LANG environment variables. gettext reads LANGUAGE directly and appends each colon-separated entry to the message catalog directory, so that fix did not cover LANGUAGE.

LANGUAGE is only used when the LC_MESSAGES locale is not "C", "C.<encoding>" or "POSIX", so the attacker must also be able to select another installed locale, for example through LANG or LC_ALL. Exploitation also requires that the attacker can place the crafted file in a location readable by the target program, and that the environment crosses a trust boundary without the program running as AT_SECURE. An example is an SSH server that accepts LANGUAGE and LANG from clients through the AcceptEnv directive and restricts an account to a forced command; the attacker may use this to escape the restriction.

Passing an effectively empty string to the ,ccs= syntax extension of the mode argument in the fopen function in the GNU C Library version 2.45 or earlier may result in a heap buffer overflow when the mode string input to the function is attacker controlled. This usage pattern is not seen in applications in common GNU/Linux distributions and applications that process user-supplied values for ccs should not pass them through without validation. (CVE-2026-18374) Stack overflow in nscd due to unbounded alloca use. (CVE-2026-89092) Assertion failure in the DNS stub resolver with a long search domain. (CVE-2026-8674) AT_SECURE programs may load attacker-controlled code via $ORIGIN. (CVE-2026-86805) AT_SECURE program buffer overflow via $ORIGIN processing. (CVE-2026-95818) Directory traversal via the LANGUAGE environment variable. (CVE-2026-84243)

Root has patched CVE-2026-84243 in the glibc package for Root:Debian:12. Multiple fixed versions available.

Root has patched CVE-2026-84243 in the glibc package for Root:Debian:13. Multiple fixed versions available.

It was discovered that the GNU C Library incorrectly handled the ccs= option in the fopen function. An attacker could possibly use this issue to cause GNU C Library to crash or execute arbitrary code. (CVE-2026-18374)

It was discovered that the GNU C Library incorrectly handled long domain names in DNS search lists. An attacker on the local network could possibly use this issue to cause GNU C Library to crash, resulting in a denial of service. (CVE-2026-8674)

It was discovered that the GNU C Library dynamic loader had a time-of-check to time-of-use race condition when handling the $ORIGIN path expansion in setuid or setgid programs. A local attacker could possibly use this issue to execute arbitrary code with elevated privileges. (CVE-2026-86805)

It was discovered that the GNU C Library dynamic loader incorrectly handled $ORIGIN path expansion, leading to a stack-based buffer overflow. A local attacker could possibly use this issue to cause GNU C Library to crash, resulting in a denial of service, or obtain sensitive information. (CVE-2026-95818)

It was discovered that the GNU C Library nscd service incorrectly handled large DNS responses. An attacker could possibly use this issue to cause nscd to crash, resulting in a denial of service. (CVE-2026-89092)

It was discovered that the GNU C Library strncasecmp function optimized for the Power8 architecture incorrectly handled certain inputs. An attacker could possibly use this issue to cause GNU C Library to crash, resulting in a denial of service. (CVE-2026-97399)

It was discovered that the GNU C Library incorrectly restricted path traversal when processing the LANGUAGE environment variable in gettext. A local attacker could possibly use this issue to load message catalogs from arbitrary locations and execute arbitrary code. (CVE-2026-84243)