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Infinite LoopWeakness · CWE-835

CVE-2026-29975

HIGH · 7.5 CVSS v3.1 Published 2026-05-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
lwjson 1.8.1 contains an improper input validation vulnerability in the streaming JSON parser (lwjson_stream.c). The end-of-string detection logic incorrectly identifies escaped quote characters by only checking the immediately preceding character rather than counting consecutive backslashes, causing valid JSON strings ending with an escaped backslash (like "\\") to never terminate parsing. A remote attacker can send well-formed JSON to cause applications using lwjson_stream_parse() to hang indefinitely, resulting in denial of service.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The lwjson streaming JSON parser in lwjson_stream.c has a flaw in end-of-string detection where it only checks the immediately preceding character to determine if a quote is escaped, rather than counting consecutive backslashes. This causes strings containing valid escaped backslashes (like '\\') at the end to never terminate, causing the parser to hang indefinitely.

MitigationUpdate to a patched version of lwjson that correctly counts consecutive backslashes when evaluating escaped quotes, or implement a fix that tracks escape sequence parity before the quote character.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate lwjson library in the environment
    Search for lwjson source files (lwjson_stream.c, lwjson.h) or binary artifacts containing 'lwjson' in the file system, or check project dependencies for lwjson
    Affected if lwjson library or its source code is present in the environment
  2. Determine the installed lwjson version
    Inspect version headers, git tags, or version macros in lwjson source files; if using a package manager, query the installed package version
    Affected if The version cannot be determined or is earlier than the patched version that fixes the backslash counting logic
  3. Identify if streaming JSON parsing is in use
    Search code for calls to streaming parser functions such as lwjson_parse_stream, lwjson_get_next_token_stream, or similar stream-based parsing APIs from lwjson
    Affected if The application uses streaming JSON parsing functions from lwjson
  4. Check for JSON input containing escaped backslashes at string endpoints
    Review JSON data sources or API inputs processed by the lwjson streaming parser for patterns where a string ends with an escaped backslash (such as '\\' before the closing quote)
    Affected if JSON input processed by the streaming parser contains strings that end with an escaped backslash sequence
  5. Verify escape sequence handling behavior
    Test the parser with a JSON input containing a string like 'test\\' (ending with escaped backslash) and observe whether parsing hangs or fails to terminate the string
    Affected if The parser fails to properly terminate a string ending with an escaped backslash and hangs or exhibits unexpected behavior

A user is affected if lwjson with a vulnerable streaming parser version processes JSON input containing strings that end with an escaped backslash sequence, causing the parser to hang indefinitely.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update to a patched version of lwjson that correctly counts consecutive backslashes when evaluating escaped quotes, or implement a fix that tracks escape sequence parity before the quote character.

Recommended fix Moderate confidence

lwjson 1.9.0 or later

  1. 1. Identify all locations in your codebase where lwjson library is used, specifically calls to lwjson_stream_parse() function.
  2. 2. Locate the lwjson library dependency in your project (check package.json, requirements.txt, CMakeLists.txt, or other dependency management files).
  3. 3. Upgrade lwjson library to version 1.9.0 or later, which contains the fix for the infinite loop vulnerability in lwjson_stream.c.
  4. 4. Rebuild and recompile your application to incorporate the updated library.
  5. 5. Test the application with JSON input containing escaped backslashes (e.g., {"path":"\\"}) to verify the fix works correctly.
  6. 6. Deploy the updated application.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-29975 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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