CVE-2022-39255

HIGHNVD 8.68.6
EchelonGraph scoreMEDIUM confidence

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

This high-severity CVE scores 8.6 under NVD CVSS v3. EPSS exploit probability: 1.0% (63rd 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
8.6EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1.0%CVSS: 8.6Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
8.6HIGHmedium confidence
EG Risk
54
EG Risk 54/100

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)
Severity86% × 45%
Impact severity (EG Severity): CVSS 8.6 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation1.0% × 40%
FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Attend at high (mission-essential systems).
Exploitation none (CISA Vulnrichment) · Automatable yes (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 at low or medium mission impact and sooner than that at high.
EPSS PROB
1.0%
EPSS %ILE
63rd
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 (8.6): severity, escalated by confirmed exploitation. This CVE's 8.6 is its impact severity (EG Severity), not escalated.

EG Severity
8.6 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
1.0% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-20). 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; Attend at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; 60 days 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 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 none (CISA Vulnrichment) · Automatable yes (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)14 days if the affected system is publicly exposed; 60 days if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable yes (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

September 28, 2022

Last Modified

November 21, 2024

Advisory Details (4)

Auto-updated Sep 1, 2026
Patch available. Sources: github_commit, github_release, github.
Web page

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 advisoryMentions a patch (unverified)

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 9× in last 7d / 34× 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 92 of 197 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. 8 repeat rows among the latest 100 are merged into the row they repeat. The 105 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-22 16:30 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
  2. 2026-10-21 16:29 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
  3. 2026-10-21 06:24 UTCEG score recompute
  4. 2026-10-20 16:29 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
  5. 2026-10-19 16:28 UTCEPSS rescoreEPSS 1.0% · 63rd percentile
  6. 2026-10-18 16:28 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
  7. 2026-10-18 08:28 UTCEG score recompute
  8. 2026-10-17 16:29 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
  9. 2026-10-16 16:35 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
  10. 2026-10-15 16:54 UTCOSV refresh
  11. 2026-10-15 16:28 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
  12. 2026-10-14 16:29 UTCEPSS rescoreEPSS 1.0% · 62nd percentile
  13. 2026-10-13 16:29 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  14. 2026-10-12 18:48 UTCEG score recompute
  15. 2026-10-12 16:30 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  16. 2026-10-11 23:12 UTCEG score recompute
  17. 2026-10-11 13:44 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  18. 2026-10-10 19:56 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  19. 2026-10-09 20:04 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  20. 2026-10-08 16:40 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  21. 2026-10-07 23:45 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  22. 2026-10-06 15:14 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  23. 2026-10-05 17:40 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  24. 2026-10-04 23:19 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  25. 2026-10-03 14:23 UTCEPSS rescoreEPSS 1.0% · 61st percentile
Show 67 more
  1. 2026-10-02 16:23 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  2. 2026-10-01 19:47 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  3. 2026-09-30 16:03 UTCEG score recompute
  4. 2026-09-30 15:00 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  5. 2026-09-29 15:16 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  6. 2026-09-27 13:42 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  7. 2026-09-26 00:22 UTCEPSS rescoreEPSS 1.0% · 61st percentile
  8. 2026-09-24 14:00 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  9. 2026-09-24 10:26 UTCOSV refresh
  10. 2026-09-22 14:45 UTCEPSS rescoreEPSS 0.8% · 56th percentile
  11. 2026-09-20 20:13 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  12. 2026-09-19 15:38 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  13. 2026-09-17 19:24 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  14. 2026-09-16 14:05 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  15. 2026-09-15 03:07 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  16. 2026-09-12 14:57 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  17. 2026-09-11 14:50 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  18. 2026-09-11 09:33 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  19. 2026-09-08 21:57 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  20. 2026-09-06 13:45 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  21. 2026-09-05 15:25 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  22. 2026-09-05 02:48 UTCOSV refresh
  23. 2026-09-04 13:57 UTCEPSS rescoreEPSS 0.8% · 55th percentile
  24. 2026-09-04 05:04 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  25. 2026-09-02 14:09 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  26. 2026-09-01 13:51 UTCEPSS rescoreEPSS 0.8% · 54th percentile
  27. 2026-08-30 19:14 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  28. 2026-08-30 01:19 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  29. 2026-08-28 21:38 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  30. 2026-08-27 14:22 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  31. 2026-08-26 14:43 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  32. 2026-08-25 13:46 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  33. 2026-08-24 14:13 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  34. 2026-08-23 00:17 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  35. 2026-08-21 23:46 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  36. 2026-08-20 22:52 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  37. 2026-08-19 17:01 UTCEPSS rescoreEPSS 0.8% · 53rd percentile
  38. 2026-08-18 13:45 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  39. 2026-08-18 13:40 UTCOSV refresh
  40. 2026-08-17 13:44 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  41. 2026-08-16 14:53 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  42. 2026-08-16 02:11 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  43. 2026-08-15 01:27 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  44. 2026-08-13 21:58 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  45. 2026-08-12 13:48 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  46. 2026-08-11 13:39 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  47. 2026-08-10 14:08 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  48. 2026-08-09 13:44 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  49. 2026-08-08 16:34 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  50. 2026-08-07 16:24 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  51. 2026-08-06 13:44 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  52. 2026-08-05 19:15 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  53. 2026-08-04 15:07 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  54. 2026-08-04 10:35 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  55. 2026-08-03 08:57 UTCOSV refresh
  56. 2026-08-02 02:24 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  57. 2026-08-01 04:13 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  58. 2026-07-30 16:25 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  59. 2026-07-30 01:28 UTCEPSS rescoreEPSS 0.8% · 52nd percentile
  60. 2026-07-28 15:33 UTCEPSS rescoreEPSS 0.8% · 51st percentile
  61. 2026-07-26 14:52 UTCEPSS rescoreEPSS 0.8% · 51st percentile
  62. 2026-07-25 14:15 UTCEPSS rescoreEPSS 0.8% · 51st percentile
  63. 2026-07-24 14:15 UTCEPSS rescoreEPSS 0.8% · 51st percentile
  64. 2026-07-23 14:16 UTCEPSS rescoreEPSS 0.8% · 51st percentile
  65. 2026-07-23 02:13 UTCEG score recompute
  66. 2026-07-22 23:00 UTCEG score recompute
  67. 2026-07-22 14:06 UTCEPSS rescoreEPSS 0.8% · 51st percentile

Frequently asked(5)

What is CVE-2022-39255?
CVE-2022-39255 is a high-severity vulnerability; its CVE record was 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 the CVE record for CVE-2022-39255 published?
The CVE record for CVE-2022-39255 was published on September 28, 2022. 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 November 21, 2024; the record at its source may have been updated since.
Is CVE-2022-39255 actively exploited?
CVE-2022-39255 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.0% probability of exploitation in the next 30 days (63rd percentile of EPSS-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?
A fix for CVE-2022-39255 is available: update to the fixed version the vendor names in its advisory.

Dependency Blast Radius

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