CVE-2026-91920
A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle…
- Risk score
- 42/100
- CVSS
- 6.5 v3.1
- Exploit chance (30 days)
- 0.2%
- Published
- 30 Oct 2026
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What to know
- What it is
- A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle chunked transfer encoding in HTTP requests. The issue occurs because a security check for the chunk size is performed before the value is shifted, allowing a specifically crafted 15-digit chunk size to bypass the limit an…
- Affected
- See advisory
- Fix
- Apply the vendor's security update; see the linked advisory.
- Exploitation
- No known exploitation
Why it is Yellow
- CVSS 6.5 medium
References
Original description
A flaw was found in the ChunkReader component of the Undertow web server, which is used to handle chunked transfer encoding in HTTP requests. The issue occurs because a security check for the chunk size is performed before the value is shifted, allowing a specifically crafted 15-digit chunk size to bypass the limit and overflow into internal state flags. This can cause the server to terminate a request body prematurely and interpret the remaining data as a separate, smuggled request.
Last activity 30 Oct 2026. Patch Forecast updates every hour.