CVE-2026-54743

MEDIUMPre-NVD 6.46.4
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to the CVSS score beside it.

This medium-severity CVE scores 6.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (45th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Elevated

Also known asEUVD-2026-62848 (ENISA EUVD)Source: ENISA EUVD

6.4EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 6.4Exploit: No code on recordExposed services: Not assessed

The CVE record names the fixed release — apply it.

Lemmy is a link aggregator and forum for the fediverse. Prior to lemmy-ui 0.19.19-beta.1, LemmyNet/lemmy-ui renders Markdown in src/shared/markdown.ts for post bodies, comment bodies, private messages, and community and site sidebars through mdToHtml, which returns a raw __html object that Inferno injects without a sanitizer pass. setupMarkdown configures html as false but registers markdown-it-html5-embed@1.0.0 with useImageSyntax enabled, so an image targeting video media becomes a video element whose fallback incorporates the image alt text through unescaped string replacement. The html setting does not apply to plugin-generated output, allowing crafted alt text to reach the DOM as live HTML in contexts that do not use mdToHtmlNoImages. An approved member or a remote federated instance can store such content, and a viewer who renders it may execute JavaScript in the lemmy-ui origin, exposing the viewer's session and authenticated actions. The advisory notes that Content Security Policy prevents the described exploit in production, but also states that the tested default self-hosted deployment serves no Content-Security-Policy. This issue is fixed in lemmy-ui version 0.19.19-beta.1.

CVSS v3
6.4
EG Score
6.4MEDIUMmedium confidence
EG Risk
45
EG Risk 45/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity64% × 45%
Impact severity (EG Severity): CVSS 6.4 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: The CVE record names the fixed release. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
45th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (6.4): severity, escalated by confirmed exploitation. This CVE's 6.4 is its impact severity (EG Severity), not escalated.

EG Severity
6.4 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
EG Likelihood
0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-24). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

The CVE record names the fixed release. Apply it within your standard update timelines.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

August 19, 2026

Last Modified

September 9, 2026

Advisory Details (3)

Auto-updated Aug 19, 2026
Fix named in the CVE record. Sources: github, github_pr, github_commit.
GitHub commit

commit 81a3fe07f2a5 (LemmyNet/lemmy-ui)

Fix landed in LemmyNet/lemmy-ui commit 81a3fe07f2a5 — awaiting tagged release

https://github.com/LemmyNet/lemmy-ui/commit/81a3fe07f2a5acc11188320534aa6bf937ebf7ff
GitHub pull request

[0.19] Swap library for markdown media embeds

Fix merged in LemmyNet/lemmy-ui PR #4213 on 2026-06-03 — awaiting tagged release

https://github.com/LemmyNet/lemmy-ui/pull/4213
GitHub advisoryMentions a patch (unverified)

Stored XSS via markdown image alt-text in lemmy-ui html5-embed · Advisory · LemmyNet/lemmy · GitHub

https://github.com/LemmyNet/lemmy/security/advisories/GHSA-2g66-9fr3-ppwj

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 43× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. 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. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 121 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 21 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  2. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  3. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  4. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  5. 2026-10-30 11:25 UTCOSV refresh
  6. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  7. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  8. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  9. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  10. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  11. 2026-10-25 14:19 UTCEG score recompute
  12. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  13. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  14. 2026-10-22 21:19 UTCEG score recompute
  15. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  16. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.5% · 45th percentile
  17. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  18. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  19. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  20. 2026-10-18 03:30 UTCEG score recompute
  21. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  22. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  23. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  24. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  25. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.5% · 44th percentile
Show 75 more
  1. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  2. 2026-10-12 15:56 UTCEG score recompute
  3. 2026-10-11 19:39 UTCEG score recompute
  4. 2026-10-11 16:54 UTCEG score recompute
  5. 2026-10-11 14:17 UTCEG score recompute
  6. 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  7. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  8. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  9. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  10. 2026-10-08 06:36 UTCEG score recompute
  11. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  12. 2026-10-07 06:37 UTCEG score recompute
  13. 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.5% · 44th percentile
  14. 2026-10-06 07:55 UTCEG score recompute
  15. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  16. 2026-10-05 05:07 UTCEG score recompute
  17. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  18. 2026-10-04 04:10 UTCEG score recompute
  19. 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  20. 2026-10-03 05:31 UTCEG score recompute
  21. 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  22. 2026-10-02 06:50 UTCEG score recompute
  23. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  24. 2026-10-01 07:17 UTCEG score recompute
  25. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  26. 2026-09-30 08:37 UTCEG score recompute
  27. 2026-09-29 15:22 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  28. 2026-09-29 03:20 UTCEG score recompute
  29. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  30. 2026-09-28 04:39 UTCEG score recompute
  31. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  32. 2026-09-27 05:57 UTCEG score recompute
  33. 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  34. 2026-09-25 02:48 UTCEG score recompute
  35. 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.5% · 43rd percentile
  36. 2026-09-24 04:08 UTCEG score recompute
  37. 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  38. 2026-09-23 05:26 UTCEG score recompute
  39. 2026-09-22 06:47 UTCEG score recompute
  40. 2026-09-21 08:06 UTCEG score recompute
  41. 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  42. 2026-09-20 09:26 UTCEG score recompute
  43. 2026-09-19 10:46 UTCEG score recompute
  44. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  45. 2026-09-18 11:52 UTCEG score recompute
  46. 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  47. 2026-09-16 14:32 UTCEG score recompute
  48. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  49. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.5% · 42nd percentile
  50. 2026-09-15 15:14 UTCEG score recompute
  51. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  52. 2026-09-13 17:36 UTCEG score recompute
  53. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  54. 2026-09-12 18:56 UTCEG score recompute
  55. 2026-09-11 20:16 UTCEG score recompute
  56. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.5% · 41st percentile
  57. 2026-09-10 21:15 UTCEG score recompute
  58. 2026-09-10 09:35 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  59. 2026-09-09 02:29 UTCEG score recompute
  60. 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  61. 2026-09-07 19:54 UTCEG score recompute
  62. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  63. 2026-09-06 21:14 UTCEG score recompute
  64. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  65. 2026-09-05 22:34 UTCEG score recompute
  66. 2026-09-04 23:54 UTCEG score recompute
  67. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  68. 2026-09-03 02:26 UTCEG score recompute
  69. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  70. 2026-09-02 03:45 UTCEG score recompute
  71. 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  72. 2026-09-01 05:04 UTCEG score recompute
  73. 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.4% · 33rd percentile
  74. 2026-08-31 06:19 UTCEG score recompute
  75. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.4% · 33rd percentile

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-54743?
CVE-2026-54743 is a medium-severity vulnerability; its CVE record was published on August 19, 2026. Lemmy is a link aggregator and forum for the fediverse. Prior to lemmy-ui 0.19.19-beta.1, LemmyNet/lemmy-ui renders Markdown in src/shared/markdown.ts for post bodies, comment bodies, private messages, and community and site sidebars through mdToHtml, which returns a raw __html object that Inferno…
When was the CVE record for CVE-2026-54743 published?
The CVE record for CVE-2026-54743 was published on August 19, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of September 9, 2026; the record at its source may have been updated since.
Is CVE-2026-54743 actively exploited?
CVE-2026-54743 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (45th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-54743?
CVE-2026-54743 has a CVSS base score of 6.4 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-54743?
The CVE record for CVE-2026-54743 names the fix: "This issue is fixed in lemmy-ui version 0.19.19-beta.1."

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