ubuntu-cve-2023-26485
Vulnerability from osv_ubuntu
Published
2023-03-31 23:15
Modified
2026-05-20 15:02
Summary
Details
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 is a fork of 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
Severity
5.3 (Medium)
7.5 (High)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cmark",
"binary_version": "0.26.1-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "cmark",
"purl": "pkg:deb/ubuntu/cmark@0.26.1-1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.26.1-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cmark",
"binary_version": "0.29.0-2"
},
{
"binary_name": "libcmark0.29.0",
"binary_version": "0.29.0-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "cmark",
"purl": "pkg:deb/ubuntu/cmark@0.29.0-2?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.28.3-1",
"0.29.0-1ubuntu2",
"0.29.0-2"
]
},
{
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "cmark-gfm",
"binary_version": "0.29.0.gfm.0-4ubuntu0.1~esm1"
},
{
"binary_name": "libcmark-gfm-extensions0",
"binary_version": "0.29.0.gfm.0-4ubuntu0.1~esm1"
},
{
"binary_name": "libcmark-gfm0",
"binary_version": "0.29.0.gfm.0-4ubuntu0.1~esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "cmark-gfm",
"purl": "pkg:deb/ubuntu/cmark-gfm@0.29.0.gfm.0-4ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.29.0.gfm.0-4ubuntu0.1~esm1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.28.3.gfm.20-3",
"0.29.0.gfm.0-3",
"0.29.0.gfm.0-4"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cmark",
"binary_version": "0.30.2-5"
},
{
"binary_name": "libcmark0.30.2",
"binary_version": "0.30.2-5"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "cmark",
"purl": "pkg:deb/ubuntu/cmark@0.30.2-5?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.29.0-4",
"0.30.2-3",
"0.30.2-4",
"0.30.2-5"
]
},
{
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "cmark-gfm",
"binary_version": "0.29.0.gfm.3-3ubuntu0.1~esm1"
},
{
"binary_name": "libcmark-gfm-extensions0.29.0.gfm.3",
"binary_version": "0.29.0.gfm.3-3ubuntu0.1~esm1"
},
{
"binary_name": "libcmark-gfm0.29.0.gfm.3",
"binary_version": "0.29.0.gfm.3-3ubuntu0.1~esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:22.04:LTS",
"name": "cmark-gfm",
"purl": "pkg:deb/ubuntu/cmark-gfm@0.29.0.gfm.3-3ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.29.0.gfm.3-3ubuntu0.1~esm1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.29.0.gfm.0-6",
"0.29.0.gfm.2-1",
"0.29.0.gfm.2-1+really.0.29.0.gfm.0ubuntu1",
"0.29.0.gfm.2-2",
"0.29.0.gfm.3-3"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cmark",
"binary_version": "0.30.2-6build1"
},
{
"binary_name": "libcmark0.30.2",
"binary_version": "0.30.2-6build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "cmark",
"purl": "pkg:deb/ubuntu/cmark@0.30.2-6build1?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.30.2-6",
"0.30.2-6build1"
]
},
{
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "cmark-gfm",
"binary_version": "0.29.0.gfm.6-6ubuntu0.24.04.1~esm1"
},
{
"binary_name": "libcmark-gfm-extensions0.29.0.gfm.6",
"binary_version": "0.29.0.gfm.6-6ubuntu0.24.04.1~esm1"
},
{
"binary_name": "libcmark-gfm0.29.0.gfm.6",
"binary_version": "0.29.0.gfm.6-6ubuntu0.24.04.1~esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:24.04:LTS",
"name": "cmark-gfm",
"purl": "pkg:deb/ubuntu/cmark-gfm@0.29.0.gfm.6-6ubuntu0.24.04.1~esm1?arch=source\u0026distro=esm-apps/noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.29.0.gfm.6-6ubuntu0.24.04.1~esm1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.29.0.gfm.6-6",
"0.29.0.gfm.6-6build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cmark",
"binary_version": "0.30.2-6build1"
},
{
"binary_name": "libcmark0.30.2",
"binary_version": "0.30.2-6build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "cmark",
"purl": "pkg:deb/ubuntu/cmark@0.30.2-6build1?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.30.2-6build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cmark",
"binary_version": "0.30.2-6build2"
},
{
"binary_name": "libcmark0.30.2",
"binary_version": "0.30.2-6build2"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "cmark",
"purl": "pkg:deb/ubuntu/cmark@0.30.2-6build2?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.30.2-6build1",
"0.30.2-6build2"
]
}
],
"aliases": [],
"details": "cmark-gfm is GitHub\u0027s 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 \u0027pad = \"_\" * 100000; print(pad + \".\" + pad, end=\"\")\u0027 | 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)",
"id": "UBUNTU-CVE-2023-26485",
"modified": "2026-05-20T15:02:31Z",
"published": "2023-03-31T23:15:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2023-26485"
},
{
"type": "REPORT",
"url": "https://github.com/github/cmark-gfm/security/advisories/GHSA-r8vr-c48j-fcc5"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2023-26485"
},
{
"type": "ADVISORY",
"url": "https://ubuntu.com/security/notices/USN-7319-1"
}
],
"related": [
"USN-7319-1"
],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2023-26485"
]
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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