CVE-2021-42574

HIGHNVD 8.38.3—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.3 under NVD CVSS v3. EPSS exploit probability: 12.2%, top 4% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Elevated
8.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 13%CVSS: 8.3Exploit: Elevated riskExposed: 0

A fix is available — apply it.

An issue was discovered in the Bidirectional Algorithm in the Unicode Specification through 14.0. It permits the visual reordering of characters via control sequences, which can be used to craft source code that renders different logic than the logical ordering of tokens ingested by compilers and interpreters. Adversaries can leverage this to encode source code for compilers accepting Unicode such that targeted vulnerabilities are introduced invisibly to human reviewers. 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 and the Unicode Bidirectional Algorithm (all versions). Due to text display behavior when text includes left-to-right and right-to-left characters, the visual order of tokens may be different from their logical order. Additionally, control characters needed to fully support the requirements of bidirectional text can further obfuscate the logical order of tokens. Unless mitigated, an adversary could craft source code such that the ordering of tokens perceived by human reviewers does not match what will be processed by a compiler/interpreter/etc. The Unicode Consortium has documented this class of 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, and in Unicode Standard Annex #31, Unicode Identifier and Pattern Syntax. Also, the BIDI specification allows applications to tailor the implementation in ways that can mitigate misleading visual reordering in program text; see HL4 in Unicode Standard Annex #9, Unicode Bidirectional Algorithm.

CVSS v3
8.3
EG Score
8.3(medium)
EG Risk
53(Track*)
EG Risk 53/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity83% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
13%
EPSS %ILE
96%
KEV
Not listed

Published

November 1, 2021

Last Modified

November 21, 2024

Advisory Details (10)

Auto-updated Sep 5, 2026
No patch confirmed yet.
generic

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

https://security.gentoo.org/glsa/202210-09
generic

[SECURITY] Fedora 34 Update: rust-1.56.1-1.fc34 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QUPA37D57VPTDLSXOOGF4UXUEADOC4PQ/
generic

[SECURITY] Fedora 35 Update: rust-1.56.1-1.fc35 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LQNTFF24ROHLVPLUOEISBN3F7QM27L4U/
generic

[SECURITY] Fedora 33 Update: rust-1.56.1-1.fc33 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IH2RG5YTR6ZZOLUV3EUPZEIJR7XHJLVD/
generic

Unicode 14.0.0

http://www.unicode.org/versions/Unicode14.0.0/
generic

oss-security - Re: Trojan Source Attacks

http://www.openwall.com/lists/oss-security/2021/11/02/10
generic

oss-security - Trojan Source Attacks

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

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

http://www.openwall.com/lists/oss-security/2021/11/01/5
generic

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

http://www.openwall.com/lists/oss-security/2021/11/01/4
generic

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

Vendor Advisories for CVE-2021-42574(14)

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

Patch Availability(30)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatllvm-toolset:rhel8-8050020211110163227.c53685002021-11-18redhat
redhatdevtoolset-11-binutils-0:2.36.1-1.el7.12021-11-18redhat
redhatdevtoolset-11-annobin-0:9.82-1.el7.12021-11-18redhat
redhatdevtoolset-10-binutils-0:2.35-5.el7.32021-11-17redhat
redhatdevtoolset-10-annobin-0:9.23-4.el7.12021-11-17redhat
redhatrust-toolset-1.54-rust-0:1.54.0-4.el7_92021-11-16redhat
redhatgcc-toolset-10-binutils-0:2.35-8.el8_5.62021-11-15redhat
redhatdevtoolset-11-gcc-0:11.2.1-1.2.el72021-11-15redhat
redhatbinutils-0:2.30-93.el8_4.22021-11-10redhat
redhatgcc-toolset-10-gcc-0:10.3.1-1.2.el8_52021-11-10redhat
redhatbinutils-0:2.30-108.el8_5.12021-11-10redhat
redhatgcc-toolset-10-annobin-0:9.29-1.el8_4.12021-11-10redhat
redhatbinutils-0:2.30-73.el8_2.12021-11-10redhat
redhatgcc-toolset-11-gcc-0:11.2.1-1.2.el8_52021-11-10redhat
redhatgcc-toolset-10-annobin-0:9.29-1.el8_5.22021-11-10redhat
redhatannobin-0:9.72-1.el8_5.22021-11-10redhat
redhatrust-toolset:rhel8-8050020211027231136.5c15747c2021-11-10redhat
redhatbinutils-0:2.30-58.el8_1.32021-11-10redhat
redhatannobin-0:8.90-1.el8_2.12021-11-10redhat
redhatgcc-toolset-10-binutils-0:2.35-8.el8_4.52021-11-10redhat
redhatgcc-toolset-11-annobin-0:9.85-1.el8_5.12021-11-10redhat
redhatannobin-0:9.50-1.el8_4.12021-11-10redhat
redhatgcc-toolset-11-binutils-0:2.36.1-1.el8_5.12021-11-10redhat
redhatgcc-0:8.5.0-4.el8_52021-11-10redhat
redhatannobin-0:8.78-1.el8_1.12021-11-10redhat
redhatbinutils-0:2.27-34.base.el7_6.42021-11-01redhat
redhatbinutils-0:2.23.52.0.1-55.el7_2.42021-11-01redhat
redhatbinutils-0:2.25.1-22.base.el7_3.32021-11-01redhat
redhatbinutils-0:2.27-44.base.el7_9.12021-11-01redhat
redhatbinutils-0:2.25.1-32.base.el7_4.52021-11-01redhat

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

(10 across 10 ecosystems)
Alpine:v3.19(1)
PackageVulnerable rangeFixed inDependents
rust—1.56.1-r0—
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
rust—1.56.1-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
rust—1.56.1-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
rust—1.56.1-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
rust—1.56.1-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
rust—1.56.1-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
rustc1.48.0+dfsg1-2 ... 1.96.0+dfsg1-1~exp1 (200 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
rustc—1.57.0+dfsg1-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
rustc—1.57.0+dfsg1-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
rustc—1.57.0+dfsg1-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(17)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 8× in last 7d / 31× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. 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. Most recent first.

Showing the most recent 100 of 159 total refreshes for this CVE.

  1. 2026-09-24 14:00 UTCEPSS rescore
  2. 2026-09-24 14:00 UTCEPSS rescore
  3. 2026-09-23 13:44 UTCEPSS rescore
  4. 2026-09-22 14:44 UTCEPSS rescore
  5. 2026-09-21 20:28 UTCEPSS rescore
  6. 2026-09-20 20:13 UTCEPSS rescore
  7. 2026-09-19 15:38 UTCEPSS rescore
  8. 2026-09-18 19:23 UTCEPSS rescore
  9. 2026-09-17 19:23 UTCEPSS rescore
  10. 2026-09-17 19:23 UTCEPSS rescore
  11. 2026-09-16 14:05 UTCEPSS rescore
  12. 2026-09-15 03:06 UTCEPSS rescore
  13. 2026-09-12 14:57 UTCEPSS rescore
  14. 2026-09-11 14:49 UTCEPSS rescore
  15. 2026-09-11 09:33 UTCEPSS rescore
  16. 2026-09-08 21:56 UTCEPSS rescore
  17. 2026-09-07 15:58 UTCEPSS rescore
  18. 2026-09-06 13:45 UTCEPSS rescore
  19. 2026-09-06 04:22 UTCOSV refresh
  20. 2026-09-05 15:25 UTCEPSS rescore
  21. 2026-09-04 13:57 UTCEPSS rescore
  22. 2026-09-04 05:03 UTCEPSS rescore
  23. 2026-09-02 14:09 UTCEPSS rescore
  24. 2026-09-01 13:50 UTCEPSS rescore
  25. 2026-09-01 03:33 UTCEPSS rescore
Show 75 more
  1. 2026-08-30 19:14 UTCEPSS rescore
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  3. 2026-08-30 01:19 UTCEPSS rescore
  4. 2026-08-28 21:37 UTCEPSS rescore
  5. 2026-08-27 14:22 UTCEPSS rescore
  6. 2026-08-26 14:43 UTCEPSS rescore
  7. 2026-08-25 13:46 UTCEPSS rescore
  8. 2026-08-24 14:13 UTCEPSS rescore
  9. 2026-08-23 00:16 UTCEPSS rescore
  10. 2026-08-21 23:46 UTCEPSS rescore
  11. 2026-08-20 22:52 UTCEPSS rescore
  12. 2026-08-20 22:52 UTCEPSS rescore
  13. 2026-08-19 17:01 UTCEPSS rescore
  14. 2026-08-19 15:29 UTCOSV refresh
  15. 2026-08-18 13:45 UTCEPSS rescore
  16. 2026-08-16 14:53 UTCEPSS rescore
  17. 2026-08-16 02:11 UTCEPSS rescore
  18. 2026-08-15 01:27 UTCEPSS rescore
  19. 2026-08-13 21:57 UTCEPSS rescore
  20. 2026-08-12 13:48 UTCEPSS rescore
  21. 2026-08-11 13:38 UTCEPSS rescore
  22. 2026-08-09 13:44 UTCEPSS rescore
  23. 2026-08-08 16:33 UTCEPSS rescore
  24. 2026-08-07 16:24 UTCEPSS rescore
  25. 2026-08-06 13:44 UTCEPSS rescore
  26. 2026-08-05 19:14 UTCEPSS rescore
  27. 2026-08-04 11:27 UTCOSV refresh
  28. 2026-08-04 10:34 UTCEPSS rescore
  29. 2026-08-03 10:33 UTCEPSS rescore
  30. 2026-08-02 02:24 UTCEPSS rescore
  31. 2026-08-01 04:13 UTCEPSS rescore
  32. 2026-07-30 16:25 UTCEPSS rescore
  33. 2026-07-30 01:28 UTCEPSS rescore
  34. 2026-07-28 15:33 UTCEPSS rescore
  35. 2026-07-26 14:52 UTCEPSS rescore
  36. 2026-07-26 14:52 UTCEPSS rescore
  37. 2026-07-25 14:15 UTCEPSS rescore
  38. 2026-07-24 14:15 UTCEPSS rescore
  39. 2026-07-23 14:16 UTCEPSS rescore
  40. 2026-07-23 02:04 UTCEG score recompute
  41. 2026-07-22 22:51 UTCEG score recompute
  42. 2026-07-22 14:06 UTCEPSS rescore
  43. 2026-07-21 15:22 UTCEPSS rescore
  44. 2026-07-21 15:22 UTCEPSS rescore
  45. 2026-07-20 17:05 UTCEPSS rescore
  46. 2026-07-19 02:27 UTCEPSS rescore
  47. 2026-07-18 10:02 UTCEPSS rescore
  48. 2026-07-18 10:02 UTCEPSS rescore
  49. 2026-07-18 08:59 UTCOSV refresh
  50. 2026-07-16 17:00 UTCEPSS rescore
  51. 2026-07-16 17:00 UTCEPSS rescore
  52. 2026-07-15 16:55 UTCEPSS rescore
  53. 2026-07-15 16:55 UTCEPSS rescore
  54. 2026-07-15 01:58 UTCEPSS rescore
  55. 2026-07-13 22:27 UTCEPSS rescore
  56. 2026-07-13 22:27 UTCEPSS rescore
  57. 2026-07-13 06:11 UTCEPSS rescore
  58. 2026-07-13 06:11 UTCEPSS rescore
  59. 2026-07-12 05:44 UTCEPSS rescore
  60. 2026-07-11 08:25 UTCEPSS rescore
  61. 2026-07-11 08:25 UTCEPSS rescore
  62. 2026-07-09 19:07 UTCEPSS rescore
  63. 2026-07-07 13:43 UTCEPSS rescore
  64. 2026-07-06 16:25 UTCEPSS rescore
  65. 2026-07-06 16:25 UTCEPSS rescore
  66. 2026-07-06 02:21 UTCEPSS rescore
  67. 2026-07-06 02:21 UTCEPSS rescore
  68. 2026-07-05 02:28 UTCEPSS rescore
  69. 2026-07-05 02:28 UTCEPSS rescore
  70. 2026-07-02 16:57 UTCEPSS rescore
  71. 2026-07-01 15:04 UTCEPSS rescore
  72. 2026-06-30 23:20 UTCEPSS rescore
  73. 2026-06-30 23:20 UTCEPSS rescore
  74. 2026-06-30 08:00 UTCOSV refresh
  75. 2026-06-28 04:54 UTCEPSS rescore

Publicly available exploits

(5 references)

Working exploit code is in the public domain (5 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCrakib-nyc/nullorigin
    First seen Aug 16, 2026

    Research-only AI watermark & provenance robustness toolkit: local reverse proxy (OpenAI/Anthropic/Gemini) + CLI stripping C2PA/EXIF/XMP, zero-width & homoglyph Unicode, KGW text watermarks, DWT/Tree-Ring image stego, AudioSeal, PDF/DOCX/PPTX/XLSX metadata, and Trojan Source (CVE-2021-42574) code scanning.

    Open source ↗
  • GitHub PoCMoshe-ship/bidi-guard
    First seen Mar 21, 2026

    Scan code for invisible bidirectional Unicode characters (Trojan Source attack prevention, CVE-2021-42574)

    Open source ↗
  • GitHub PoCtin-z/solidity_CVE-2021-42574-POC
    First seen Jan 31, 2023

    POC of CVE-2021-42574 for solidity and solc compiler

    Open source ↗
  • GitHub PoCmaweil/bidi_char_detector
    First seen Nov 6, 2021

    Checks your files for existence of Unicode BIDI characters which can be misused for supply chain attacks. See CVE-2021-42574

    Open source ↗
  • GitHub PoCsimplylu/CVE-2021-42574
    First seen Nov 2, 2021

    Generate malicious files using recently published bidi-attack (CVE-2021-42574)

    Open source ↗

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2021-42574?
CVE-2021-42574 is a high vulnerability published on November 1, 2021. An issue was discovered in the Bidirectional Algorithm in the Unicode Specification through 14.0. It permits the visual reordering of characters via control sequences, which can be used to craft source code that renders different logic than the logical ordering of tokens ingested by compilers and…
When was CVE-2021-42574 disclosed?
CVE-2021-42574 was first published in the National Vulnerability Database on November 1, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-42574 actively exploited?
CVE-2021-42574 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 13% probability of exploitation in the next 30 days, which ranks it in the top 3.8% of all scored CVEs.
What is the CVSS score of CVE-2021-42574?
CVE-2021-42574 has a CVSS v3 base score of 8.3 (NVD).
How do I remediate CVE-2021-42574?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-42574, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-42574

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