CVE-2026-0818

MEDIUMNVD 4.34.3—
EchelonGraph scoreMEDIUM confidence

Score 4.3 from GitHub Security Advisory published 2026-01-28. NVD baseline CVSS 4.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
4.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 4.3Exploit: NoneExposed: 0

A fix is available — apply it.

When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If the user had additionally allowed loading of the remote content referenced by the outer email message, and the email was crafted by the sender using a combination of CSS rules and fonts and animations, then it was possible to extract the secret contents of the email. This vulnerability was fixed in Thunderbird 147.0.1 and Thunderbird 140.7.1.

CVSS v3
4.3
EG Score
4.3(medium)
EPSS
5.5%
KEV
Not listed

Published

January 28, 2026

Last Modified

April 13, 2026

References (4)

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuxul-ext-lightning (1:140.7.1+build1-0ubuntu0.22.04.1) @ jammy2026-06-08ubuntu

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.

Weakness Classification(3)

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 / 32× 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.

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-0818?
CVE-2026-0818 is a medium vulnerability published on January 28, 2026. When a user explicitly requested Thunderbird to decrypt an inline OpenPGP message that was embedded in a text section of an email that was formatted and styled with HTML and CSS, then the decrypted contents were rendered in a context in which the CSS styles from the outer messages were active. If…
When was CVE-2026-0818 disclosed?
CVE-2026-0818 was first published in the National Vulnerability Database on January 28, 2026, with the most recent update on April 13, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-0818 actively exploited?
CVE-2026-0818 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 5.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-0818?
CVE-2026-0818 has a CVSS v3 base score of 4.3 (NVD).
How do I remediate CVE-2026-0818?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-0818, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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