CVE-2021-42694

HIGHNVD 8.38.3
EchelonGraph scoreMEDIUM confidence

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

Score 8.3 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 8.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 3 sources updated this weekElevated
8.3EG
EchelonGraph verdictPlan mitigationRemediate within your standard update timelines at low or medium mission impact and sooner than that at high (the SSVC decision on this page).
  • Public exploit or proof-of-concept code is available
CISA-KEV: Not listedEPSS PROB: 4.9%CVSS: 8.3Exploit: Public PoCExposed services: Not assessed

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

CISA-ADP, in the CVE record, lists unicode versions before 14.0.0 as affected. No release containing a fix is confirmed on record.

An issue was discovered in the character definitions of the Unicode Specification through 14.0. The specification allows an adversary to produce source code identifiers such as function names using homoglyphs that render visually identical to a target identifier. Adversaries can leverage this to inject code via adversarial identifier definitions in upstream software dependencies invoked deceptively in downstream software. NOTE: the Unicode Consortium offers the following alternative approach to presenting this concern. An issue is noted in the nature of international text that can affect applications that implement support for The Unicode Standard (all versions). Unless mitigated, an adversary could produce source code identifiers using homoglyph characters that render visually identical to but are distinct from a target identifier. In this way, an adversary could inject adversarial identifier definitions in upstream software that are not detected by human reviewers and are invoked deceptively in downstream software. The Unicode Consortium has documented this class of security vulnerability in its document, Unicode Technical Report #36, Unicode Security Considerations. The Unicode Consortium also provides guidance on mitigations for this class of issues in Unicode Technical Standard #39, Unicode Security Mechanisms.

CVSS v3
8.3
EG Score
8.3HIGHmedium confidence
EG Risk
53
EG Risk 53/100

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)
Severity83% × 45%
Impact severity (EG Severity): CVSS 8.3 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low, Track* at medium and Attend at high mission impact.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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: No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.
EPSS PROB
4.9%
EPSS %ILE
92nd
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 (8.3): severity, escalated by confirmed exploitation. This CVE's 8.3 is its impact severity (EG Severity), not escalated.

EG Severity
8.3 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
EG Likelihood
4.9% 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, Track* at medium and Attend at high mission impact.CISA BOD 26-04: 14 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 low, Track* at medium and Attend at high mission impact.

No fix is confirmed yet. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines at low or medium mission impact and sooner than that at high, and watch the vendor's advisory for the fix.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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; Fix on system upgrade if it is not.

In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (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

November 1, 2021

Last Modified

November 21, 2024

Advisory Details (10)

Auto-updated Sep 6, 2026
No fix on record yet. Sources: cert.
Web page

UTS #39: Unicode Security Mechanisms

https://www.unicode.org/reports/tr39/
Web page

Stabilized Technical Report

https://www.unicode.org/reports/tr36/
Web page

Trojans in your source code - JDriven Blog

https://www.scyon.nl/post/trojans-in-your-source-code
CERT

VU#999008 - Compilers permit Unicode control and homoglyph characters

https://www.kb.cert.org/vuls/id/999008
Web page

Trojan Source Attacks

https://trojansource.codes
Web page

Rust: Multiple Vulnerabilities (GLSA 202210-09) — Gentoo security

https://security.gentoo.org/glsa/202210-09
Web page

CWE - CWE-1007: Insufficient Visual Distinction of Homoglyphs Presented to User (4.20)

https://cwe.mitre.org/data/definitions/1007.html
Web page

oss-security - Trojan Source Attacks

http://www.openwall.com/lists/oss-security/2021/11/01/6
Web page

oss-security - CVE-2021-42574: rustc 1.56.0 and bidirectional-override codepoints in source code

http://www.openwall.com/lists/oss-security/2021/11/01/1

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 36× 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 95 of 194 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. 5 repeat rows among the latest 100 are merged into the row they repeat. The 99 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-10-23 16:28 UTCEPSS rescoreEPSS 4.9% · 92nd percentile
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  3. 2026-10-21 16:28 UTCEPSS rescoreEPSS 4.9% · 92nd percentile
  4. 2026-10-21 08:54 UTCEG score recompute
  5. 2026-10-21 08:54 UTCGHSA enrichmentGHSA-m3pq-m926-j2h4 · GitHub severity CRITICAL · GitHub CVSS 8.3
  6. 2026-10-20 16:28 UTCEPSS rescoreEPSS 4.9% · 92nd percentile
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Publicly available exploits

(1 reference)

Public exploit code is referenced for this CVE (1 GitHub PoC). No fix is confirmed yet, so defenders should restrict or isolate affected systems accordingly until one is published.

  • GitHub PoCsimplylu/CVE-2021-42694
    Published Nov 2, 2021

    Generate malicious files using recently published homoglyphic-attack (CVE-2021-42694)

    Open source ↗

Frequently asked(5)

What is CVE-2021-42694?
CVE-2021-42694 is a high-severity vulnerability; its CVE record was published on November 1, 2021. An issue was discovered in the character definitions of the Unicode Specification through 14.0. The specification allows an adversary to produce source code identifiers such as function names using homoglyphs that render visually identical to a target identifier. Adversaries can leverage this to…
When was the CVE record for CVE-2021-42694 published?
The CVE record for CVE-2021-42694 was published on November 1, 2021. 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-2021-42694 actively exploited?
CVE-2021-42694 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 4.9% probability of exploitation in the next 30 days (92nd percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2021-42694?
CVE-2021-42694 has a CVSS v3 base score of 8.3 (NVD).
How do I remediate CVE-2021-42694?
No fix for CVE-2021-42694 is confirmed yet. Until one is published, restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and watch the vendor's advisory for the fix. CISA-ADP, in the CVE record, lists unicode versions before 14.0.0 as affected. No release containing a fix is confirmed on record.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2021-42694

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