5.3

CVE-2026-63435: mikel mail Interpretation Conflict

CVSS: 5.3v3.1MediumDeferred
AliasesUBUNTU-CVE-2026-63435DEBIAN-CVE-2026-63435CGA-3m93-56jr-fm2c
Published 01-09-2026Last modified 02-09-2026
Open JSON

Vulnerability summary

CVE-2026-63435 is a medium (CVSS 5.3) Interpretation Conflict vulnerability in mikel mail. EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 37.6% of scored vulnerabilities.

Overall risk
21/100
0100
Low · default modelHow is this calculated?
CVSS score
5.3/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.45%
0%100%
Low · +0.12 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 1
CGA-G54W-QGW3-99M7

Timeline

  1. 01-09-2026
    PublishedVulnerability first disclosed.
  2. 02-09-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

0.45%

Chance of exploitation in the next 30 days

Percentile

38%

Versus all other CVEs

30-day change

+0.12 pp

From 0.33% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.45%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard41 products
  • commercial-gitlab-rails-ee-19.1All versions (No fix recorded)
  • commercial-gitlab-rails-ee-19.2< 19.2.7-r4
  • commercial-gitlab-rails-ee-19.3< 19.3.3-r4
  • commercial-gitlab-rails-ee-19.4< 19.4.1-r3
  • commercial-gitlab-rails-ee-fips-19.1All versions (No fix recorded)
Ubuntu7 products
  • jrubyAll versions (No fix recorded)
  • ruby2.3All versions (No fix recorded)
  • ruby2.5All versions (No fix recorded)
  • ruby2.7All versions (No fix recorded)
  • ruby3.0All versions (No fix recorded)
Wolfi3 products
  • ruby3.2-kube-logging-operator-fluentd-outputs< 6.8.0-r6
  • ruby3.3-mail< 2.9.1-r0
  • ruby3.4-kube-logging-operator-fluentd-outputs< 6.8.0-r6
Debian1 product
  • ruby-mailAll versions (No fix recorded) | < 2.9.1-1
Mikel1 product
RubyGems1 product
  • mail< 2.9.1

6 vendors · 54 products

References

10 links