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CVE-2023-28631

Attacker controlled data in AST nodes is not validated in comrak

5.3 MediumFix available

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

1.27%Up 1.2 points since Mar 29, 2023
90%50%10%1%

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 MediumCVSS: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 MediumCVSS: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] and Vec<u8> fields in the AST.

References

n/a

Record
GHSA-5r3x-p7xx-x6q5
CVSS 3.1
5.3 MediumCVSS: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 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS 3.1
9.8 CriticalCVSS: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 MediumCVSS: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] and Vec<u8> fields in the AST.

References

n/a

Record
GHSA-5r3x-p7xx-x6q5
CVSS 3.1
5.3 MediumCVSS: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

Affected packages
PackageAffectedFixed
comrak
crates.io
before 0.17.0
0.17.0

History

History
RecordedChangedSources
first indexedCVE 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

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