CVE-2026-27469

MEDIUMNVD 6.16.1
EchelonGraph scoreMEDIUM confidence

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

This medium-severity CVE scores 6.1 under NVD CVSS v3. EPSS exploit probability: 0.4% (35th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
6.1EG
EchelonGraph verdictMonitorRemediate within your standard update timelines (the SSVC decision on this page).
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 6.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

Isso is a lightweight commenting server written in Python and JavaScript. In commits before 0afbfe0691ee237963e8fb0b2ee01c9e55ca2144, there is a stored Cross-Site Scripting (XSS) vulnerability affecting the website and author comment fields. The website field was HTML-escaped using quote=False, which left single and double quotes unescaped. Since the frontend inserts the website value directly into a single-quoted href attribute via string concatenation, a single quote in the URL breaks out of the attribute context, allowing injection of arbitrary event handlers (e.g. onmouseover, onclick). The same escaping is missing entirely from the user-facing comment edit endpoint (PUT /id/) and the moderation edit endpoint (POST /id//edit/). This issue has been patched in commit 0afbfe0691ee237963e8fb0b2ee01c9e55ca2144. To workaround, nabling comment moderation (moderation = enabled = true in isso.cfg) prevents unauthenticated users from publishing comments, raising the bar for exploitation, but it does not fully mitigate the issue since a moderator activating a malicious comment would still expose visitors.

CVSS v3
6.1
EG Score
6.1MEDIUMmedium confidence
EG Risk
28
EG Risk 28/100

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)
Severity61% × 45%
Impact severity (EG Severity): CVSS 6.1 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.4% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at every mission impact level.
Exploitation none (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: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.4%
EPSS %ILE
35th
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 (6.1): severity, escalated by confirmed exploitation. This CVE's 6.1 is its impact severity (EG Severity), not escalated.

EG Severity
6.1 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.4% within 30 daysSource: FIRST EPSS. 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 every mission impact level.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: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (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.

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

February 21, 2026

Last Modified

June 17, 2026

Advisory Details (3)

Auto-updated Aug 6, 2026
Patch available. Sources: github, github_commit.
GitHub advisoryMentions a patch (unverified)

Stored XSS via comment website field · Advisory · isso-comments/isso · GitHub

https://github.com/isso-comments/isso/security/advisories/GHSA-9fww-8cpr-q66r
GitHub commit Patch Available

commit 0afbfe0691ee (isso-comments/isso)

Patch available: isso-comments/isso 0.14.0 (contains commit 0afbfe0691ee)

https://github.com/isso-comments/isso/commit/0afbfe0691ee237963e8fb0b2ee01c9e55ca2144
Web page

html — HyperText Markup Language support — Python 3.14.7 documentation

https://docs.python.org/3/library/html.html#html.escape

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
isso0.10 ... 0.9.9 (34 versions)
  • every version up to 0.13.2: fixed in 0.13.2
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 30× 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 93 of 202 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. 7 repeat rows among the latest 100 are merged into the row they repeat. The 109 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-21 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  2. 2026-10-20 16:32 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  3. 2026-10-19 16:31 UTCEPSS rescoreEPSS 0.4% · 35th percentile
  4. 2026-10-18 16:31 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  5. 2026-10-18 03:51 UTCEG score recompute
  6. 2026-10-17 16:33 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  7. 2026-10-16 16:41 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  8. 2026-10-15 16:31 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  9. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.4% · 30th percentile
  10. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  11. 2026-10-12 16:33 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  12. 2026-10-12 16:17 UTCEG score recompute
  13. 2026-10-11 19:59 UTCEG score recompute
  14. 2026-10-11 17:13 UTCEG score recompute
  15. 2026-10-11 14:44 UTCEG score recompute
  16. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  17. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 29th percentile
  18. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  19. 2026-10-08 17:11 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  20. 2026-10-08 14:24 UTCOSV refresh
  21. 2026-10-07 23:47 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  22. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  23. 2026-10-05 17:42 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  24. 2026-10-04 23:21 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  25. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.4% · 28th percentile
Show 68 more
  1. 2026-10-01 19:49 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  2. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  3. 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  4. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  5. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.4% · 28th percentile
  6. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.2% · 13th percentile
  7. 2026-09-18 20:06 UTCOSV refresh
  8. 2026-09-18 19:27 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  9. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  10. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  11. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  12. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  13. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  14. 2026-09-11 14:52 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  15. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  16. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  17. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  18. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  19. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  20. 2026-09-02 14:11 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  21. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  22. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  23. 2026-08-30 23:03 UTCOSV refresh
  24. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  25. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  26. 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  27. 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  28. 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  29. 2026-08-25 13:48 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  30. 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  31. 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  32. 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  33. 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  34. 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  35. 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  36. 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  37. 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  38. 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  39. 2026-08-14 09:17 UTCEG score recompute
  40. 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  41. 2026-08-13 02:20 UTCEG score recompute
  42. 2026-08-12 13:50 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  43. 2026-08-12 01:28 UTCEG score recompute
  44. 2026-08-11 13:42 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  45. 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  46. 2026-08-10 09:46 UTCEG score recompute
  47. 2026-08-09 13:46 UTCEPSS rescoreEPSS 0.2% · 11th percentile
  48. 2026-08-09 08:55 UTCEG score recompute
  49. 2026-08-08 16:37 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  50. 2026-08-07 21:03 UTCEG score recompute
  51. 2026-08-06 13:46 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  52. 2026-08-06 03:15 UTCEG score recompute
  53. 2026-08-05 19:17 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  54. 2026-08-04 15:10 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  55. 2026-08-03 10:36 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  56. 2026-08-02 19:51 UTCEG score recompute
  57. 2026-08-02 02:26 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  58. 2026-08-01 04:16 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  59. 2026-07-30 16:27 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  60. 2026-07-30 01:30 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  61. 2026-07-28 15:36 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  62. 2026-07-26 14:54 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  63. 2026-07-25 14:17 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  64. 2026-07-24 14:17 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  65. 2026-07-23 14:18 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  66. 2026-07-23 03:08 UTCEG score recompute
  67. 2026-07-22 14:08 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  68. 2026-07-21 15:24 UTCEPSS rescoreEPSS 0.2% · 12th percentile

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-27469?
CVE-2026-27469 is a medium-severity vulnerability; its CVE record was published on February 21, 2026. Isso is a lightweight commenting server written in Python and JavaScript. In commits before 0afbfe0691ee237963e8fb0b2ee01c9e55ca2144, there is a stored Cross-Site Scripting (XSS) vulnerability affecting the website and author comment fields. The website field was HTML-escaped using quote=False,…
When was the CVE record for CVE-2026-27469 published?
The CVE record for CVE-2026-27469 was published on February 21, 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 June 17, 2026; the record at its source may have been updated since.
Is CVE-2026-27469 actively exploited?
CVE-2026-27469 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (35th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-27469?
CVE-2026-27469 has a CVSS v3 base score of 6.1 (NVD).
How do I remediate CVE-2026-27469?
A fix for CVE-2026-27469 is available: update to the fixed version the vendor names in its advisory.

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