CVE-2022-39255

HIGHNVD 8.68.6—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.6 under NVD CVSS v3. EPSS exploit probability: 0.8%, top 49% of all CVEs by exploit prediction. 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
8.6EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 8.6Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages that legitimately appear to have come from another person, without any indication such as a grey shield. Additionally, a sophisticated attacker cooperating with a malicious homeserver could employ this vulnerability to perform a targeted attack in order to send fake to-device messages appearing to originate from another user. This can allow, for example, to inject the key backup secret during a self-verification, to make a targeted device start using a malicious key backup spoofed by the homeserver. These attacks are possible due to a protocol confusion vulnerability that accepts to-device messages encrypted with Megolm instead of Olm. matrix-ios-sdk version 0.23.19 has been modified to only accept Olm-encrypted to-device messages. Out of caution, several other checks have been audited or added. This attack requires coordination between a malicious home server and an attacker, so those who trust their home servers do not need a workaround. To avoid malicious backup attacks, one should not verify one's new logins using emoji/QR verifications methods until patched.

CVSS v3
8.6
EG Score
8.6(medium)
EG Risk
54(Track)
EG Risk 54/100SSVC: Track

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
Severity86% × 45%
Exploitation1% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
1%
EPSS %ILE
55%
KEV
Not listed

Published

September 28, 2022

Last Modified

November 21, 2024

Advisory Details (4)

Auto-updated Sep 1, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: github_commit, github_release, github.
generic🔴 Active Exploitation

Matrix.org - Upgrade now to address E2EE vulnerabilities in matrix-js-sdk, matrix-ios-sdk and matrix-android-sdk2

https://matrix.org/blog/2022/09/28/upgrade-now-to-address-encryption-vulns-in-matrix-sdks-and-clients
github Patch Available

Olm/Megolm protocol confusion · Advisory · matrix-org/matrix-ios-sdk · GitHub

https://github.com/matrix-org/matrix-ios-sdk/security/advisories/GHSA-hw6g-j8v6-9hcm
github_release Patch Available

Release v0.23.19 (matrix-org/matrix-ios-sdk)

Patch available: matrix-org/matrix-ios-sdk v0.23.19

https://github.com/matrix-org/matrix-ios-sdk/releases/tag/v0.23.19
github_commit Patch Available

commit 5ca86c328a5f (matrix-org/matrix-ios-sdk)

Patch available: matrix-org/matrix-ios-sdk v0.26.3 (contains commit 5ca86c328a5f)

https://github.com/matrix-org/matrix-ios-sdk/commit/5ca86c328a5faaab429c240551cb9ca8f0f6262c

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 7× in last 7d / 31× 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 160 total refreshes for this CVE.

  1. 2026-09-06 13:45 UTCEPSS rescore
  2. 2026-09-05 15:25 UTCEPSS rescore
  3. 2026-09-05 02:48 UTCOSV refresh
  4. 2026-09-04 13:57 UTCEPSS rescore
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  20. 2026-08-18 13:45 UTCEPSS rescore
  21. 2026-08-18 13:40 UTCOSV refresh
  22. 2026-08-17 13:44 UTCEPSS rescore
  23. 2026-08-16 14:53 UTCEPSS rescore
  24. 2026-08-16 02:11 UTCEPSS rescore
  25. 2026-08-15 01:27 UTCEPSS rescore
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  1. 2026-08-13 21:58 UTCEPSS rescore
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  3. 2026-08-12 13:48 UTCEPSS rescore
  4. 2026-08-11 13:39 UTCEPSS rescore
  5. 2026-08-10 14:08 UTCEPSS rescore
  6. 2026-08-09 13:44 UTCEPSS rescore
  7. 2026-08-08 16:34 UTCEPSS rescore
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  9. 2026-08-06 13:44 UTCEPSS rescore
  10. 2026-08-05 19:15 UTCEPSS rescore
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  12. 2026-08-04 15:07 UTCEPSS rescore
  13. 2026-08-04 10:35 UTCEPSS rescore
  14. 2026-08-03 08:57 UTCOSV refresh
  15. 2026-08-02 02:24 UTCEPSS rescore
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  17. 2026-07-30 16:25 UTCEPSS rescore
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  19. 2026-07-30 01:28 UTCEPSS rescore
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  26. 2026-07-23 14:16 UTCEPSS rescore
  27. 2026-07-23 02:13 UTCEG score recompute
  28. 2026-07-22 23:00 UTCEG score recompute
  29. 2026-07-22 14:06 UTCEPSS rescore
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  37. 2026-07-18 10:03 UTCEPSS rescore
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  39. 2026-07-16 18:49 UTCOSV refresh
  40. 2026-07-16 17:00 UTCEPSS rescore
  41. 2026-07-15 16:56 UTCEPSS rescore
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  43. 2026-07-15 01:58 UTCEPSS rescore
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  45. 2026-07-13 22:28 UTCEPSS rescore
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  47. 2026-07-13 06:11 UTCEPSS rescore
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  49. 2026-07-12 05:44 UTCEPSS rescore
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  51. 2026-07-11 08:25 UTCEPSS rescore
  52. 2026-07-09 19:08 UTCEPSS rescore
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  54. 2026-07-07 13:44 UTCEPSS rescore
  55. 2026-07-06 16:25 UTCEPSS rescore
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  65. 2026-06-29 14:04 UTCEPSS rescore
  66. 2026-06-28 17:02 UTCOSV refresh
  67. 2026-06-28 14:06 UTCEPSS rescore
  68. 2026-06-28 04:54 UTCEPSS rescore
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  70. 2026-06-27 03:07 UTCEPSS rescore
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  72. 2026-06-25 13:48 UTCEPSS rescore
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  74. 2026-06-24 14:03 UTCEPSS rescore
  75. 2026-06-24 14:03 UTCEPSS rescore

Frequently asked(5)

What is CVE-2022-39255?
CVE-2022-39255 is a high vulnerability published on September 28, 2022. Matrix iOS SDK allows developers to build iOS apps compatible with Matrix. Prior to version 0.23.19, an attacker cooperating with a malicious homeserver can construct messages that legitimately appear to have come from another person, without any indication such as a grey shield. Additionally, a…
When was CVE-2022-39255 disclosed?
CVE-2022-39255 was first published in the National Vulnerability Database on September 28, 2022, 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-2022-39255 actively exploited?
CVE-2022-39255 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 44.9% of all scored CVEs.
What is the CVSS score of CVE-2022-39255?
CVE-2022-39255 has a CVSS v3 base score of 8.6 (NVD).
How do I remediate CVE-2022-39255?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2022-39255, 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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