XML::Parser versions through 2.47 for Perl has an off-by-one heap buffer overflow in st_serial_stack.
In the case (stackptr == stacksize - 1), the stack will NOT be expanded. Then the new value will be written at location (++stackptr), which equals stacksize and therefore falls just outside the allocated buffer.
The bug can be observed when parsing an XML file with very deep element nesting
Weakness
A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Xml::parser | Toddr | * | 2.48 (excluding) |
| Red Hat Enterprise Linux 10 | RedHat | perl-XML-Parser-0:2.47-6.1.el10_1 | * |
| Red Hat Enterprise Linux 10.0 Extended Update Support | RedHat | perl-XML-Parser-0:2.47-6.el10_0.1 | * |
| Red Hat Enterprise Linux 7 Extended Lifecycle Support | RedHat | perl-XML-Parser-0:2.41-10.el7_9.1 | * |
| Red Hat Enterprise Linux 8 | RedHat | perl-XML-Parser-0:2.44-12.el8_10 | * |
| Red Hat Enterprise Linux 8.2 Advanced Update Support | RedHat | perl-XML-Parser-0:2.44-11.el8_2.1 | * |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | RedHat | perl-XML-Parser-0:2.44-11.el8_4.1 | * |
| Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | RedHat | perl-XML-Parser-0:2.44-11.el8_4.1 | * |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | RedHat | perl-XML-Parser-0:2.44-11.el8_6.1 | * |
| Red Hat Enterprise Linux 8.6 Telecommunications Update Service | RedHat | perl-XML-Parser-0:2.44-11.el8_6.1 | * |
| Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions | RedHat | perl-XML-Parser-0:2.44-11.el8_6.1 | * |
| Red Hat Enterprise Linux 8.8 Telecommunications Update Service | RedHat | perl-XML-Parser-0:2.44-11.el8_8.1 | * |
| Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions | RedHat | perl-XML-Parser-0:2.44-11.el8_8.1 | * |
| Red Hat Enterprise Linux 9 | RedHat | perl-XML-Parser-0:2.46-9.1.el9_7 | * |
| Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions | RedHat | perl-XML-Parser-0:2.46-9.el9_0.1 | * |
| Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions | RedHat | perl-XML-Parser-0:2.46-9.el9_2.1 | * |
| Red Hat Enterprise Linux 9.4 Extended Update Support | RedHat | perl-XML-Parser-0:2.46-9.el9_4.1 | * |
| Red Hat Enterprise Linux 9.6 Extended Update Support | RedHat | perl-XML-Parser-0:2.46-9.el9_6.1 | * |
| Libxml-parser-perl | Ubuntu | esm-infra/xenial | * |
| Libxml-parser-perl | Ubuntu | jammy | * |
| Libxml-parser-perl | Ubuntu | noble | * |
| Libxml-parser-perl | Ubuntu | questing | * |
Potential Mitigations
- Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
- D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
- Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
- Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
- For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Related Attack Patterns
References
- https://github.com/cpan-authors/XML-Parser/commit/3eb9cc95420fa0c3f76947c4708962546bf27cfd.patch
- https://github.com/cpan-authors/XML-Parser/issues/39
- https://rt.cpan.org/Ticket/Display.html?id=19860
- http://www.openwall.com/lists/oss-security/2026/03/19/2
- https://lists.debian.org/debian-lts-announce/2026/04/msg00002.html