CommonMarker versions prior to 0.23.4 are at risk of an integer overflow vulnerability. This vulnerability can result in possibly unauthenticated remote attackers to cause heap memory corruption, potentially leading to an information leak or remote code execution, via parsing tables with marker rows that contain more than UINT16_MAX columns.

cmark-gfm is an extended version of the C reference implementation of CommonMark, a rationalized version of Markdown syntax with a spec. Three polynomial time complexity issues in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. These vulnerabilities have been patched in 0.29.0.gfm.12.

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. This CVE covers quadratic complexity issues when parsing text which leads with either large numbers of `_` characters. This issue has been addressed in version 0.29.0.gfm.10. Users are advised to upgrade. Users unable to upgrade should validate that their input comes from trusted sources. ### Impact A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. ### Proof of concept ``` $ ~/cmark-gfm$ python3 -c 'pad = "_" * 100000; print(pad + "." + pad, end="")' | time ./build/src/cmark-gfm --to plaintext ``` Increasing the number 10000 in the above commands causes the running time to increase quadratically. ### Patches This vulnerability have been patched in 0.29.0.gfm.10. ### Note on cmark and cmark-gfm XXX: TBD [cmark-gfm](https://github.com/github/cmark-gfm) is a fork of [cmark](https://github.com/commonmark/cmark) that adds the GitHub Flavored Markdown extensions. The two codebases have diverged over time, but share a common core. These bugs affect both `cmark` and `cmark-gfm`. ### Credit We would like to thank @gravypod for reporting this vulnerability. ### References https://en.wikipedia.org/wiki/Time_complexity ### For more information If you have any questions or comments about this advisory: * Open an issue in [github/cmark-gfm](https://github.com/github/cmark-gfm)

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. A polynomial time complexity issue in cmark-gfm may lead to unbounded resource exhaustion and subsequent denial of service. This CVE covers quadratic complexity issues when parsing text which leads with either large numbers of `>` or `-` characters. This issue has been addressed in version 0.29.0.gfm.10. Users are advised to upgrade. Users unable to upgrade should validate that their input comes from trusted sources.

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. Versions prior to 0.29.0.gfm.7 contain a polynomial time complexity issue in handle_close_bracket that may lead to unbounded resource exhaustion and subsequent denial of service. This vulnerability has been patched in 0.29.0.gfm.7.

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. In versions prior 0.29.0.gfm.7, a crafted markdown document can trigger an out-of-bounds read in the `validate_protocol` function. We believe this bug is harmless in practice, because the out-of-bounds read accesses `malloc` metadata without causing any visible damage.This vulnerability has been patched in 0.29.0.gfm.7.

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. Versions prior to 0.29.0.gfm.7 are subject to a polynomial time complexity issue in cmark-gfm that may lead to unbounded resource exhaustion and subsequent denial of service. This vulnerability has been patched in 0.29.0.gfm.7.

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. Versions prior to 0.29.0.gfm.7 are subject to several polynomial time complexity issues in cmark-gfm that may lead to unbounded resource exhaustion and subsequent denial of service. Various commands, when piped to cmark-gfm with large values, cause the running time to increase quadratically. These vulnerabilities have been patched in version 0.29.0.gfm.7.

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. In versions prior to 0.29.0.gfm.6 a polynomial time complexity issue in cmark-gfm's autolink extension may lead to unbounded resource exhaustion and subsequent denial of service. Users may verify the patch by running `python3 -c 'print("![l"* 100000 + "\n")' | ./cmark-gfm -e autolink`, which will resource exhaust on unpatched cmark-gfm but render correctly on patched cmark-gfm. This vulnerability has been patched in 0.29.0.gfm.6. Users are advised to upgrade. Users unable to upgrade should disable the use of the autolink extension.

cmark-gfm is GitHub's extended version of the C reference implementation of CommonMark. Prior to versions 0.29.0.gfm.3 and 0.28.3.gfm.21, an integer overflow in cmark-gfm's table row parsing `table.c:row_from_string` may lead to heap memory corruption when parsing tables who's marker rows contain more than UINT16_MAX columns. The impact of this heap corruption ranges from Information Leak to Arbitrary Code Execution depending on how and where `cmark-gfm` is used. If `cmark-gfm` is used for rendering remote user controlled markdown, this vulnerability may lead to Remote Code Execution (RCE) in applications employing affected versions of the `cmark-gfm` library. This vulnerability has been patched in the following cmark-gfm versions 0.29.0.gfm.3 and 0.28.3.gfm.21. A workaround is available. The vulnerability exists in the table markdown extensions of cmark-gfm. Disabling the table extension will prevent this vulnerability from being triggered.