CVE-2026-11979

libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process. This issue has been fixed in the commit c2e233fc. NOTE: The maintainers of this project did not agree that this issue is a vulnerability and considered it a bug.

This library allows to manipulate XML files. It includes support to read, modify and write XML and HTML files. There is DTDs support this includes parsing and validation even with complex DtDs, either at parse time or later once the document has been modified. The output can be a simple SAX stream or and in-memory DOM like representations. In this case one can use the built-in XPath and XPointer implementation to select sub nodes or ranges. A flexible Input/Output mechanism is available, with existing HTTP and FTP modules and combined to an URI library.

Security Fix(es):

libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process.

This issue has been fixed in the commit c2e233fc.

NOTE: The maintainers of this project did not agree that this issue is a vulnerability and considered it a bug.(CVE-2026-11979)

The libxml2 library is a development toolbox providing the implementation of various XML standards.

Security Fix(es):

• libxml2: libxml2: Arbitrary code execution in xmlcatalog utility via buffer overflow (CVE-2026-11979)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The libxml2 library is a development toolbox providing the implementation of various XML standards.

Security Fix(es):

• libxml2: mingw-libxml2: libxml2: Denial of Service via crafted XML input due to use-after-free (CVE-2026-6653)

• libxml2: libxml2: Arbitrary code execution in xmlcatalog utility via buffer overflow (CVE-2026-11979)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The libxml2 library is a development toolbox providing the implementation of various XML standards.

Security Fix(es):

• libxml2: libxml2: Arbitrary code execution in xmlcatalog utility via buffer overflow (CVE-2026-11979)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

libxml2 is vulnerable to multiple stack-based buffer overflows in the xmlcatalog utility when running in --shell mode. The usershell() function processes user input using fixed-size stack buffers without proper bounds checking. By supplying an overly long input line, an attacker can overflow internal buffers (command, arg, and argv) during input parsing. This results in memory corruption within the stack frame. Successful exploitation may cause a crash or potentially allow arbitrary code execution in the context of the xmlcatalog process. This issue has been fixed in the commit c2e233fc. NOTE: The maintainers of this project did not agree that this issue is a vulnerability and considered it a bug.

The libxml2 library is a development toolbox providing the implementation of various XML standards.

Security Fix(es):

• libxml2: libxml2: Arbitrary code execution in xmlcatalog utility via buffer overflow (CVE-2026-11979)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The libxml2 library is a development toolbox providing the implementation of various XML standards.

Security Fix(es):

• libxml2: mingw-libxml2: libxml2: Denial of Service via crafted XML input due to use-after-free (CVE-2026-6653)
• libxml2: libxml2: Arbitrary code execution in xmlcatalog utility via buffer overflow (CVE-2026-11979)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

The libxml2 library is a development toolbox providing the implementation of various XML standards.

Security Fix(es):

• libxml2: libxml2: Arbitrary code execution in xmlcatalog utility via buffer overflow (CVE-2026-11979)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

• CVE-2026-11979: add bounds checks in xmlcatalog usershell() to prevent stack-based buffer overflow on long --shell input

• SECURITY UPDATE: stack-based buffer overflows in the xmlcatalog utility interactive --shell mode
  • debian/patches/CVE-2026-11979.patch: Add bounds checks in usershell() in xmlcatalog.c so the command, arg and argv fixed-size stack buffers are not overflowed by an overly long --shell input line
  • CVE-2026-11979

• CVE-2026-11979: add overflow checks for large xmlcatalog --shell commands in usershell()

• SECURITY UPDATE: buffer overflow in xmlcatalog --shell interactive mode
  • debian/patches/CVE-2026-11979.patch: add overflow checks for large commands, args and argv in usershell() in xmlcatalog.c
  • CVE-2026-11979

• CVE-2026-11979: add bounds checks in xmlcatalog --shell usershell() to prevent stack buffer overflows when parsing overly long command lines

• CVE-2026-11979: add bounds checks in xmlcatalog --shell usershell() to prevent stack buffer overflows when parsing overly long command lines

• SECURITY UPDATE: stack buffer overflows in xmlcatalog --shell mode
  • debian/patches/CVE-2026-11979.patch: add bounds checks in the usershell() command-line parser in xmlcatalog.c to prevent stack buffer overflows when parsing overly long command lines
  • CVE-2026-11979

• SECURITY UPDATE: stack buffer overflows in xmlcatalog --shell mode
  • debian/patches/CVE-2026-11979.patch: add bounds checks in the usershell() command-line parser in xmlcatalog.c to prevent stack buffer overflows when parsing overly long command lines
  • CVE-2026-11979

• CVE-2026-11979: add bounds checks in xmlcatalog --shell usershell() to prevent stack buffer overflows when parsing overly long command lines

• CVE-2026-11979: add bounds checks in xmlcatalog --shell usershell() to prevent stack buffer overflows when parsing overly long command lines

• CVE-2026-11979: add bounds checks in xmlcatalog --shell usershell() to prevent stack buffer overflows when parsing overly long command lines

• CVE-2026-11979.patch: add overflow checks for large xmlcatalog --shell commands in usershell()

• CVE-2026-11979.patch: add overflow checks for large xmlcatalog --shell commands in usershell()

• CVE-2026-11979: add bounds checks in xmlcatalog usershell() to prevent stack-based buffer overflow on long --shell input

The updated packages fix several security issues: Stack-Based Buffer Overflow in libxml2. (CVE-2026-11979) In libxml2 before 2.15.4, xmlFAParsePosCharGroup has an out-of-bounds read, aka an out-of-bounds read in the NXT macro in xmlregexp. (CVE-2026-86137) In libxml2 before 2.15.4, xmlDictAddQString in dict.c has an integer overflow and resultant heap-based buffer overflow. (CVE-2026-86138) In libxml2 before 2.15.4, xmlURIEscapeStr in uri.c has an integer overflow. (CVE-2026-86139) In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow. (CVE-2026-86140) xmlregexp in libxml2 before 2.15.4 has a NULL pointer dereference in xmlRegNewParserCtxt after a strdup failure, i.e., it does not calculate a string length after NULL checking. (CVE-2026-86141) In libxml2 before 2.15.4, there is a heap-based buffer overflow in xmlXPtrEvalXPtrPart because of xmlXPtrEval xpointer length saturation. (CVE-2026-86142) In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and xmlBufUse causes negative lengths to reach write callbacks, aka a lack of a check for integer overflow before calling writecallback. This has security relevance for many types of uses of that length value within a callback. (CVE-2026-86143) In xinclude in libxml2 before 2.15.4, xmlXIncludeProcess and xmlXIncludeProcessTree do not propagate parseFlags. This has security relevance for, for example, the XML_PARSE_NONET flag, if (without it) a custom resource loader accesses the internet and triggers XML external entity injection, SSRF, or a denial of service (e.g., for an attacker-controlled internet resource that is intentionally slow). (CVE-2026-86144)

These are all security issues fixed in the libxml2-16-2.15.3-2.1 package on the GA media of openSUSE Tumbleweed.

This update for libxml2 fixes the following issues

• CVE-2026-6732: crafted XSD-validated document can cause a denial of service (bsc#1262719).
• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issues

• CVE-2026-6732: crafted XSD-validated document can cause a denial of service (bsc#1262719).
• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issues

• CVE-2026-6732: crafted XSD-validated document can cause a denial of service (bsc#1262719).
• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issue

• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issue

• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issue

• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issue

• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issue

• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).

This update for libxml2 fixes the following issue

• CVE-2026-11979: stack-based buffer overflows in the xmlcatalog utility when running in --shell mode (bsc#1269790).