CVE-2023-28631
Attacker controlled data in AST nodes is not validated in comrak
comrak is a CommonMark + GFM compatible Markdown parser and renderer written in rust. A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case. Version 0.17.0 contains adjustments to the AST, storing strings instead of unvalidated byte arrays. Users are advised to upgrade. Users unable to upgrade may manually validate UTF-8 correctness of all data when assigning to &[u8] and Vec<u8> fields in the AST. This issue is also tracked as GHSL-2023-049.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
5.3
Attacker controlled data in AST nodes is not validated in comrak
comrak is a CommonMark + GFM compatible Markdown parser and renderer written in rust. A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case. Version 0.17.0 contains adjustments to the AST, storing strings instead of unvalidated byte arrays. Users are advised to upgrade. Users unable to upgrade may manually validate UTF-8 correctness of all data when assigning to &[u8] and Vec<u8> fields in the AST. This issue is also tracked as GHSL-2023-049.
- Record
CVE-2023-28631- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-755
- Updated
- 2026-11-02
EUVDEUVD-2023-0886
5.3
comrak is a CommonMark + GFM compatible Markdown parser and renderer written in rust. A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case. Version 0.17.0 contains adjustments to the AST, storing strings instead of unvalidated byte arrays. Users are advised to upgrade. Users unable to upgrade may manually validate UTF-8 correctness of all data when assigning to &[u8] and Vec<u8> fields in the AST. This issue is also tracked as GHSL-2023-049.
- Record
EUVD-2023-0886- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-5r3x-p7xx-x6q5
5.3
Comrak AST node data is not validated (GHSL-2023-049)
Impact
A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case.
Patches
0.17.0 contains adjustments to the AST, storing strings instead of unvalidated byte arrays.
Workarounds
- Validate UTF-8 correctness of all data when assigning to
&[u8]andVec<u8>fields in the AST.
References
n/a
- Record
GHSA-5r3x-p7xx-x6q5- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-755
- Updated
- 2026-11-02
NVD
5.3
comrak is a CommonMark + GFM compatible Markdown parser and renderer written in rust. A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case. Version 0.17.0 contains adjustments to the AST, storing strings instead of unvalidated byte arrays. Users are advised to upgrade. Users unable to upgrade may manually validate UTF-8 correctness of all data when assigning to &[u8] and Vec<u8> fields in the AST. This issue is also tracked as GHSL-2023-049.
- Record
CVE-2023-28631- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-755
- Updated
- 2026-11-02
OSV
5.3
Attacker controlled data in AST nodes is not validated in comrak
comrak is a CommonMark + GFM compatible Markdown parser and renderer written in rust. A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case. Version 0.17.0 contains adjustments to the AST, storing strings instead of unvalidated byte arrays. Users are advised to upgrade. Users unable to upgrade may manually validate UTF-8 correctness of all data when assigning to &[u8] and Vec<u8> fields in the AST. This issue is also tracked as GHSL-2023-049.
- Record
CVE-2023-28631- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-755
- Updated
- 2026-11-02
OSVGHSA-5r3x-p7xx-x6q5
5.3
Comrak AST node data is not validated (GHSL-2023-049)
Impact
A Comrak AST can be constructed manually by a program instead of parsing a Markdown document with parse_document. This AST can then be converted to HTML via html::format_document_with_plugins. However, the HTML formatting code assumes that the AST is well-formed. For example, many AST notes contain [u8] fields which the formatting code assumes is valid UTF-8 data. Several bugs can be triggered if this is not the case.
Patches
0.17.0 contains adjustments to the AST, storing strings instead of unvalidated byte arrays.
Workarounds
- Validate UTF-8 correctness of all data when assigning to
&[u8]andVec<u8>fields in the AST.
References
n/a
- Record
GHSA-5r3x-p7xx-x6q5- CVSS 3.1
- 5.3 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-755
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
comrakcrates.io |
before 0.17.0 | 0.17.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-28631 is a medium vulnerability (CVSS 5.3) in Comrak Project Comrak, published March 28, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.27%, the 69th percentile. Fixed in comrak 0.17.0.
References
github.com/kivikakk/comrak/security/advisories/GHSA-5r3x-p7xx-x6q5
github.com/kivikakk/comrak/commit/9ff5f8df0ac951f5742d22a72c39b89a15f56639
lists.fedoraproject.org/archives/list/[email protected]/message/PTWZWCT7KCX2KTXTLPUYZ3EHOONG4X46
lists.fedoraproject.org/archives/list/[email protected]/message/OUYME2VA555X6567H7ORIJQFN4BVGT6N
lists.fedoraproject.org/archives/list/[email protected]/message/VQ3UBC7LE4VPCMZBTADIBL353CH7CPVV
github.com/kivikakk/comrak/releases/tag/0.17.0