CVE-2026-40203

LOWPre-NVD 3.73.7
EchelonGraph scoreMEDIUM confidence

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

Score 3.7 from GitHub Security Advisory (severity: LOW) published 2026-08-28. A secondary CVSS source baseline 3.7; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, a secondary CVSS source
3.7EG
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: 0.3%CVSS: 3.7Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can confirm whether the body of a small message matches a guessed text. Recovery of arbitrary unknown content was not demonstrated, but the attack can disclose whether a secret-like message body matches a candidate. Disable IMAP compression. Update to non-vulnerable version. No publicly available exploits are known.

CVSS v3
3.7
EG Score
3.7LOWmedium confidence
EG Risk
17
EG Risk 17/100

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)
Severity37% × 45%
Impact severity (EG Severity): CVSS 3.7 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation0.3% × 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
0.3%
EPSS %ILE
16th
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 (3.7): severity, escalated by confirmed exploitation. This CVE's 3.7 is its impact severity (EG Severity), not escalated.

EG Severity
3.7 LOWCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
0.3% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-17). 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

August 28, 2026

Last Modified

September 3, 2026

References (1)

Vendor Advisories for CVE-2026-40203(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(5 across 5 ecosystems)
Alpine:v3.23(1)
PackageVulnerable rangeFix by version rangeDependents
dovecot—
  • every version up to 2.4.5-r0: fixed in 2.4.5-r0
—
Alpine:v3.24(1)
PackageVulnerable rangeFix by version rangeDependents
dovecot—
  • every version up to 2.4.5-r0: fixed in 2.4.5-r0
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
dovecot1:2.3.19.1+dfsg1-2.1 ... 1:2.4.5+dfsg1-3 (43 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
dovecot1:2.4.1+dfsg1-6 ... 1:2.4.1+dfsg1-6+deb13u6 (7 versions)
  • every version up to 1:2.4.1+dfsg1-6+deb13u7: fixed in 1:2.4.1+dfsg1-6+deb13u7
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
dovecot1:2.4.1+dfsg1-6 ... 1:2.4.4+dfsg1-2 (12 versions)
  • every version up to 1:2.4.5+dfsg1-1: fixed in 1:2.4.5+dfsg1-1
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 8× in last 7d / 42× 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.

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. 1 repeat row among the latest 86 is merged into the row it repeats.

  1. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  2. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  3. 2026-10-18 03:43 UTCEG score recompute
  4. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  5. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  6. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  7. 2026-10-14 16:32 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  8. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  9. 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  10. 2026-10-12 16:09 UTCEG score recompute
  11. 2026-10-11 19:52 UTCEG score recompute
  12. 2026-10-11 17:05 UTCEG score recompute
  13. 2026-10-11 14:31 UTCEG score recompute
  14. 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  15. 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 16th percentile
  16. 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  17. 2026-10-09 02:42 UTCEG score recompute
  18. 2026-10-09 02:42 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  19. 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  20. 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  21. 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  22. 2026-10-06 09:14 UTCEG score recompute
  23. 2026-10-06 09:14 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  24. 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  25. 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 15th percentile
Show 60 more
  1. 2026-10-03 16:02 UTCEG score recompute
  2. 2026-10-03 16:02 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  3. 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  4. 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  5. 2026-09-30 22:34 UTCEG score recompute
  6. 2026-09-30 22:34 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  7. 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  8. 2026-09-28 05:15 UTCEG score recompute
  9. 2026-09-28 05:15 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  10. 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  11. 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  12. 2026-09-26 00:26 UTCEPSS rescoreEPSS 0.3% · 17th percentile
  13. 2026-09-25 12:03 UTCEG score recompute
  14. 2026-09-25 12:03 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  15. 2026-09-22 18:51 UTCEG score recompute
  16. 2026-09-22 18:50 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  17. 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  18. 2026-09-20 01:38 UTCEG score recompute
  19. 2026-09-20 01:38 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  20. 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  21. 2026-09-17 19:30 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  22. 2026-09-17 08:25 UTCEG score recompute
  23. 2026-09-17 08:25 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  24. 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  25. 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  26. 2026-09-15 03:11 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  27. 2026-09-14 15:12 UTCEG score recompute
  28. 2026-09-14 15:12 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  29. 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  30. 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  31. 2026-09-11 22:00 UTCEG score recompute
  32. 2026-09-11 22:00 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  33. 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  34. 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  35. 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  36. 2026-09-09 04:47 UTCEG score recompute
  37. 2026-09-09 04:47 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  38. 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  39. 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  40. 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  41. 2026-09-06 11:34 UTCEG score recompute
  42. 2026-09-06 11:34 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  43. 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  44. 2026-09-03 18:21 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  45. 2026-09-03 03:05 UTCEG score recompute
  46. 2026-09-03 03:04 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  47. 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  48. 2026-09-01 13:53 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  49. 2026-09-01 04:39 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  50. 2026-08-31 09:49 UTCEG score recompute
  51. 2026-08-31 09:49 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  52. 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  53. 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 12th percentile
  54. 2026-08-28 16:36 UTCEG score recompute
  55. 2026-08-28 16:36 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  56. 2026-08-28 15:39 UTCEG score recompute
  57. 2026-08-28 15:38 UTCGHSA enrichmentGHSA-cf77-42mj-h39j · GitHub severity LOW · GitHub CVSS 3.7
  58. 2026-08-28 12:23 UTCEG score recompute
  59. 2026-08-28 11:25 UTCEG score recomputeFirst assessed: 3.7 LOW
  60. 2026-08-28 11:19 UTCMITRE cvelistV5first tracked

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Frequently asked(5)

What is CVE-2026-40203?
CVE-2026-40203 is a low-severity vulnerability; its CVE record was published on August 28, 2026. When IMAP compression is enabled, the same compression state is reused across responses in a session, so response sizes depend on both attacker-supplied mail and other mail in the same mailbox. An attacker that can send mail to a user and can also observe the sizes of that user's IMAP traffic can…
When was the CVE record for CVE-2026-40203 published?
The CVE record for CVE-2026-40203 was published on August 28, 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 3, 2026; the record at its source may have been updated since.
Is CVE-2026-40203 actively exploited?
CVE-2026-40203 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (16th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-40203?
CVE-2026-40203 has a CVSS base score of 3.7 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-40203?
A fix for CVE-2026-40203 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-40203 are linked in the Vendor Advisories panel on this page.

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