Mail is an internet library for Ruby designed to handle email generation, parsing, and sending. Prior to 2.9.1, Mail::Utilities.q_value_decode and Mail::Utilities.b_value_decode used a single String#match and an overly greedy charset capture to decode only the first RFC 2047 encoded-word and mishandle surrounding or subsequent text. A crafted malformed encoded-word in an address display name or local part could cross ? delimiters and make decoded From, To, or Reply-To header values differ from the raw values inspected by a human reviewer or downstream parser, enabling apparent sender or recipient spoofing, phishing, or authorization-check bypass. This issue is fixed in version 2.9.1.
CVE-2026-63435
“—” beside the score: it is equal to the CVSS score beside it.
Score 5.3 from GitHub Security Advisory (severity: MODERATE) published 2026-09-02. A secondary CVSS source baseline 5.3; sources differ by 0.0.
Also known asEUVD-2026-69609 (ENISA EUVD) · GHSA-mvxr-6m87-mv2q (GitHub Security Advisories)Source: ENISA EUVD
- Lower severity and no public exploit yet
A fix is available — apply it.
- CVSS v3
- 5.3
- EG Score
- 5.3MEDIUMmedium confidence
- EG Risk
- 39EG Risk 39/100
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)Severity53% × 45%Impact severity (EG Severity): CVSS 5.3 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.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
- 0.4%
- EPSS %ILE
- 38th
- 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 (5.3): severity, escalated by confirmed exploitation. This CVE's 5.3 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.3 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-31). 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, and whom BOD 26-04 binds: 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.
The score's inputs: 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 1, 2026
Last Modified
September 9, 2026
Advisory Details (4)
Auto-updated Sep 1, 20262.9.1
Patch available: mikel/mail 2.9.1
https://github.com/mikel/mail/releases/tag/2.9.1commit f9d59c2e447a (mikel/mail)
Patch available: mikel/mail 2.9.1 (contains commit f9d59c2e447a)
https://github.com/mikel/mail/commit/f9d59c2e447af42e2c3dec5a56b1bb25c7292859Improve decoding of Q- and B-encoded strings
Patch available: mikel/mail 2.9.1 (PR #1664 merged 2026-07-01)
https://github.com/mikel/mail/pull/1664Email address spoofing via malformed RFC 2047 encoded-words in mail · Advisory · mikel/mail · GitHub
https://github.com/mikel/mail/security/advisories/GHSA-mvxr-6m87-mv2qVendor Advisories for CVE-2026-63435(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Patch Availability(1)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| rubygems | mail @ 2.9.1 (fixes < 2.9.1) | — | ghsa |
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.
Affected Packages
(4 across 4 ecosystems)
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ruby-mail | 2.7.1+dfsg1-2, 2.8.1+dfsg1-1, 2.8.1+dfsg1-2, 2.9.0+dfsg1-1, 2.9.1-1 |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ruby-mail | 2.8.1+dfsg1-2, 2.9.0+dfsg1-1, 2.9.1-1 |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| ruby-mail | 2.8.1+dfsg1-2, 2.9.0+dfsg1-1 |
| — |
RubyGems(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| 1.0.0 ... 2.9.0.beta2 (96 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 46× 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.
- 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-11-01 16:35 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-11-01 07:41 UTCGHSA enrichmentGHSA-mvxr-6m87-mv2q · GitHub severity MODERATE · GitHub CVSS 5.3
- 2026-11-01 07:41 UTCEG score recompute
- 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-30 08:55 UTCOSV refresh
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-25 14:13 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.4% · 38th percentile
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-22 19:49 UTCEG score recompute
- 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-18 03:23 UTCEG score recompute
- 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-16 16:43 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.4% · 37th percentile
Show 73 moreShow fewer
- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-12 15:49 UTCEG score recompute
- 2026-10-11 19:33 UTCEG score recompute
- 2026-10-11 16:48 UTCEG score recompute
- 2026-10-11 14:10 UTCEG score recompute
- 2026-10-11 13:49 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.4% · 37th percentile
- 2026-10-10 00:03 UTCEG score recompute
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-09 01:53 UTCEG score recompute
- 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-08 00:05 UTCEG score recompute
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-06 16:28 UTCEG score recompute
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-05 18:28 UTCEG score recompute
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-03 22:38 UTCEG score recompute
- 2026-10-03 14:26 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-03 00:26 UTCEG score recompute
- 2026-10-02 17:56 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-02 01:13 UTCEG score recompute
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-10-01 02:46 UTCEG score recompute
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-09-30 04:51 UTCEG score recompute
- 2026-09-29 06:45 UTCEG score recompute
- 2026-09-28 13:51 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-09-28 08:50 UTCEG score recompute
- 2026-09-27 10:54 UTCEG score recompute
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.4% · 36th percentile
- 2026-09-26 12:32 UTCEG score recompute
- 2026-09-25 11:18 UTCEG score recompute
- 2026-09-24 12:34 UTCEG score recompute
- 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.3% · 26th percentile
- 2026-09-22 16:40 UTCEG score recompute
- 2026-09-20 20:47 UTCEG score recompute
- 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.3% · 26th percentile
- 2026-09-19 22:52 UTCEG score recompute
- 2026-09-19 00:57 UTCEG score recompute
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.3% · 26th percentile
- 2026-09-18 03:01 UTCEG score recompute
- 2026-09-17 05:05 UTCEG score recompute
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-16 07:09 UTCEG score recompute
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-15 09:13 UTCEG score recompute
- 2026-09-14 11:17 UTCEG score recompute
- 2026-09-12 15:27 UTCEG score recompute
- 2026-09-11 17:27 UTCEG score recompute
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-10 19:06 UTCEG score recompute
- 2026-09-09 02:20 UTCEG score recompute
- 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-08 04:18 UTCEG score recompute
- 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-07 06:22 UTCEG score recompute
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-06 08:23 UTCEG score recompute
- 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-05 10:27 UTCEG score recompute
- 2026-09-04 12:32 UTCEG score recompute
- 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-02 16:38 UTCEG score recompute
- 2026-09-02 15:53 UTCEG score recompute
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.3% · 25th percentile
- 2026-09-01 21:27 UTCEG score recompute
- 2026-09-01 20:23 UTCEG score recomputeFirst assessed: 5.3 MEDIUM
- 2026-09-01 20:22 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same CWE)
Same product
4 shownDebian:12:ruby-mail · RubyGems:mail
Frequently asked(5)
What is CVE-2026-63435?
When was the CVE record for CVE-2026-63435 published?
Is CVE-2026-63435 actively exploited?
What is the CVSS score of CVE-2026-63435?
How do I remediate CVE-2026-63435?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-63435
Is Your Infrastructure Affected by CVE-2026-63435?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.