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CVE detail

CVE-2021-42574

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 8.3 · HighBuzz score 25.6

Buzz score

Why this CVE is surfacing

Buzz score total 25.6

This all-time snapshot uses the same composite formula as Trending across a 30-year evidence window, rather than a current rolling window.

Buzz score components · mention 16.1 · diversity 9.5 · KEV 0.0 · OTX 0.0 · PoC 0.0
Mention score
16.1
4 evidence mentions in the snapshot
Diversity score
9.5
4 sources across 1 categories
KEV score
0.0
No KEV entry observed
OTX score
0.0
0 OTX pulses
PoC score
0.0
0 repos · best confidence N/A
Best PoC traction
0
Maximum stars on a matched PoC repo

Why it matters now

Mention timeline

Total mentions
0
within the 30d window
Peak daily
0
highest bucket

Evidence

Source links by recency

Newest mentions first
4 source links · newest first
  • Trojan Source: Hiding malicious code in plain sightMalwarebytes Labs

    Researchers at the University of Cambridge, UK, have released details of a cunning and insidious new class of software vulnerability that…

    newswww.malwarebytes.comNov 2, 2021, 5:00 PM
  • Trojan Source attack method allows hiding flaws in source codeSecurity Affairs

    Researchers devised a new attack method called ‘Trojan Source’ that allows hide vulnerabilities into the source code of a software project. Trojan Source is a new attack technique demonstrated by a group of Cambridge researchers that can allow threat actors to hide vulnerabilities in the source code of a software project. The technique could be […]

    newssecurityaffairs.comNov 2, 2021, 11:54 AM
  • Trojan Source bugs may lead to extensive supply-chain attacks on source codeHelp Net Security

    Cambridge University researchers have detailed a new way targeted vulnerabilities can be introduced into source code while making them invisible to human code reviewers, allowing for extensive supply-chain attacks. “We have discovered ways of manipulating the encoding of source code files so that human viewers and compilers see different logic. One particularly pernicious method uses Unicode directionality override characters to display code as an anagram of its true logic,” professor Ross Anderson explained. The Trojan … More →

    newswww.helpnetsecurity.comNov 2, 2021, 10:51 AM
  • ‘Trojan Source’ Attack Abuses Unicode to Inject Vulnerabilities Into CodeSecurityWeek

    Researchers from the University of Cambridge have identified a new attack method that abuses Unicode to stealthily inject vulnerabilities into code.

    newswww.securityweek.comNov 1, 2021, 3:46 PM

Exploit code

Public exploit repository references

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0 repository references · best confidence N/A · max 0 stars
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