CVE-2023-26485

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.3 under NVD CVSS v3. EPSS exploit probability: 1.0% (62nd percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 1.0%CVSS: 5.3Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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

CVSS v3
5.3
EG Score
5.3MEDIUMmedium confidence
EG Risk
55
EG Risk 55/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation40% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
1.0%
EPSS %ILE
62nd
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

March 31, 2023

Last Modified

November 21, 2024

References (4)

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
ubuntulibcmark-gfm0 (0.29.0.gfm.0-4ubuntu0.1~esm1) @ focal2026-05-25ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(16 across 4 ecosystems)
Debian:11(4)
PackageVulnerable rangeFix by version rangeDependents
cmark-gfm0.29.0.gfm.0-6 ... 0.29.0.gfm.6-6 (16 versions)
  • every version on: no fix on record
—
python-cmarkgfm0.4.2-1 ... 2025.10.22-2 (8 versions)
  • every version on: no fix on record
—
r-cran-commonmark1.7-2 ... 2.0.0-2 (10 versions)
  • every version on: no fix on record
—
ruby-commonmarker0.21.0-1 ... 2.8.3-1 (11 versions)
  • every version on: no fix on record
—
Debian:12(4)
PackageVulnerable rangeFix by version rangeDependents
cmark-gfm0.29.0.gfm.13-1 ... 0.29.0.gfm.6-6 (7 versions)
  • every version on: no fix on record
—
python-cmarkgfm0.8.0-3, 2024.11.20-1, 2025.10.22-1, 2025.10.22-2
  • every version on: no fix on record
—
r-cran-commonmark1.8.1-1 ... 2.0.0-3 (9 versions)
  • every version on: no fix on record
—
ruby-commonmarker0.23.10-1 ... 2.8.3-4 (9 versions)
  • every version on: no fix on record
—
Debian:13(4)
PackageVulnerable rangeFix by version rangeDependents
cmark-gfm—
  • every version up to 0.29.0.gfm.13-1: fixed in 0.29.0.gfm.13-1
—
python-cmarkgfm—
  • every version up to 2024.11.20-1: fixed in 2024.11.20-1
—
r-cran-commonmark—
  • every version up to 1.9.1-1: fixed in 1.9.1-1
—
ruby-commonmarker—
  • every version up to 0.23.10-1: fixed in 0.23.10-1
—
Debian:14(4)
PackageVulnerable rangeFix by version rangeDependents
cmark-gfm—
  • every version up to 0.29.0.gfm.13-1: fixed in 0.29.0.gfm.13-1
—
python-cmarkgfm—
  • every version up to 2024.11.20-1: fixed in 2024.11.20-1
—
r-cran-commonmark—
  • every version up to 1.9.1-1: fixed in 1.9.1-1
—
ruby-commonmarker—
  • every version up to 0.23.10-1: fixed in 0.23.10-1
—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(1)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 25× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 188 total refreshes for this CVE.

  1. 2026-10-09 20:05 UTCEPSS rescore
  2. 2026-10-08 17:06 UTCEPSS rescore
  3. 2026-10-07 23:45 UTCEPSS rescore
  4. 2026-10-06 15:15 UTCEPSS rescore
  5. 2026-10-05 17:41 UTCEPSS rescore
  6. 2026-10-04 23:20 UTCEPSS rescore
  7. 2026-10-03 14:23 UTCEPSS rescore
  8. 2026-10-02 16:23 UTCEPSS rescore
  9. 2026-10-01 19:47 UTCEPSS rescore
  10. 2026-09-30 16:19 UTCEG score recompute
  11. 2026-09-30 15:01 UTCEPSS rescore
  12. 2026-09-29 15:16 UTCEPSS rescore
  13. 2026-09-28 13:49 UTCEPSS rescore
  14. 2026-09-27 13:42 UTCEPSS rescore
  15. 2026-09-26 00:22 UTCEPSS rescore
  16. 2026-09-24 14:01 UTCEPSS rescore
  17. 2026-09-23 16:34 UTCOSV refresh
  18. 2026-09-23 13:45 UTCEPSS rescore
  19. 2026-09-22 14:45 UTCEPSS rescore
  20. 2026-09-20 20:14 UTCEPSS rescore
  21. 2026-09-16 14:05 UTCEPSS rescore
  22. 2026-09-13 16:44 UTCEPSS rescore
  23. 2026-09-12 14:58 UTCEPSS rescore
  24. 2026-09-11 14:50 UTCEPSS rescore
  25. 2026-09-11 09:34 UTCEPSS rescore
Show 75 more
  1. 2026-09-08 21:57 UTCEPSS rescore
  2. 2026-09-07 15:59 UTCEPSS rescore
  3. 2026-09-06 13:45 UTCEPSS rescore
  4. 2026-09-05 15:25 UTCEPSS rescore
  5. 2026-09-04 13:58 UTCEPSS rescore
  6. 2026-09-04 11:16 UTCOSV refresh
  7. 2026-09-04 05:04 UTCEPSS rescore
  8. 2026-09-02 14:09 UTCEPSS rescore
  9. 2026-09-01 13:51 UTCEPSS rescore
  10. 2026-08-30 19:15 UTCEPSS rescore
  11. 2026-08-30 01:19 UTCEPSS rescore
  12. 2026-08-28 21:38 UTCEPSS rescore
  13. 2026-08-27 14:23 UTCEPSS rescore
  14. 2026-08-26 14:43 UTCEPSS rescore
  15. 2026-08-25 13:46 UTCEPSS rescore
  16. 2026-08-24 14:14 UTCEPSS rescore
  17. 2026-08-23 00:17 UTCEPSS rescore
  18. 2026-08-21 23:46 UTCEPSS rescore
  19. 2026-08-20 22:53 UTCEPSS rescore
  20. 2026-08-19 17:02 UTCEPSS rescore
  21. 2026-08-18 13:46 UTCEPSS rescore
  22. 2026-08-17 21:59 UTCOSV refresh
  23. 2026-08-17 13:44 UTCEPSS rescore
  24. 2026-08-16 14:53 UTCEPSS rescore
  25. 2026-08-16 02:12 UTCEPSS rescore
  26. 2026-08-15 01:28 UTCEPSS rescore
  27. 2026-08-13 21:58 UTCEPSS rescore
  28. 2026-08-12 13:48 UTCEPSS rescore
  29. 2026-08-11 13:39 UTCEPSS rescore
  30. 2026-08-09 13:44 UTCEPSS rescore
  31. 2026-08-08 16:34 UTCEPSS rescore
  32. 2026-08-07 16:24 UTCEPSS rescore
  33. 2026-08-06 13:44 UTCEPSS rescore
  34. 2026-08-05 19:15 UTCEPSS rescore
  35. 2026-08-05 19:15 UTCEPSS rescore
  36. 2026-08-04 15:07 UTCEPSS rescore
  37. 2026-08-04 10:35 UTCEPSS rescore
  38. 2026-08-03 10:34 UTCEPSS rescore
  39. 2026-08-02 17:27 UTCOSV refresh
  40. 2026-08-02 02:25 UTCEPSS rescore
  41. 2026-08-02 02:24 UTCEPSS rescore
  42. 2026-08-01 04:13 UTCEPSS rescore
  43. 2026-08-01 04:13 UTCEPSS rescore
  44. 2026-07-30 16:26 UTCEPSS rescore
  45. 2026-07-30 16:26 UTCEPSS rescore
  46. 2026-07-30 01:28 UTCEPSS rescore
  47. 2026-07-30 01:28 UTCEPSS rescore
  48. 2026-07-28 15:34 UTCEPSS rescore
  49. 2026-07-28 15:34 UTCEPSS rescore
  50. 2026-07-27 14:10 UTCEPSS rescore
  51. 2026-07-26 14:52 UTCEPSS rescore
  52. 2026-07-26 14:52 UTCEPSS rescore
  53. 2026-07-25 14:16 UTCEPSS rescore
  54. 2026-07-24 14:15 UTCEPSS rescore
  55. 2026-07-23 14:16 UTCEPSS rescore
  56. 2026-07-23 14:16 UTCEPSS rescore
  57. 2026-07-23 02:20 UTCEG score recompute
  58. 2026-07-22 23:08 UTCEG score recompute
  59. 2026-07-22 14:06 UTCEPSS rescore
  60. 2026-07-22 14:06 UTCEPSS rescore
  61. 2026-07-21 15:23 UTCEPSS rescore
  62. 2026-07-20 17:06 UTCEPSS rescore
  63. 2026-07-19 14:29 UTCEPSS rescore
  64. 2026-07-19 14:29 UTCEPSS rescore
  65. 2026-07-19 02:27 UTCEPSS rescore
  66. 2026-07-19 02:27 UTCEPSS rescore
  67. 2026-07-18 10:03 UTCEPSS rescore
  68. 2026-07-18 10:03 UTCEPSS rescore
  69. 2026-07-16 17:01 UTCEPSS rescore
  70. 2026-07-16 17:01 UTCEPSS rescore
  71. 2026-07-16 01:19 UTCOSV refresh
  72. 2026-07-15 16:56 UTCEPSS rescore
  73. 2026-07-15 16:56 UTCEPSS rescore
  74. 2026-07-15 01:58 UTCEPSS rescore
  75. 2026-07-15 01:58 UTCEPSS rescore

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Frequently asked(5)

What is CVE-2023-26485?
CVE-2023-26485 is a medium vulnerability published on March 31, 2023. 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…
When was CVE-2023-26485 disclosed?
CVE-2023-26485 was first published on March 31, 2023, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-26485 actively exploited?
CVE-2023-26485 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.0% probability of exploitation in the next 30 days (62nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2023-26485?
CVE-2023-26485 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2023-26485?
A fix for CVE-2023-26485 is available: update to the fixed version the vendor names in its advisory.

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