Medium [CVE-2026-66338] http request smuggling via permissive chunk-size parsing in soup_body_input_stream_read_chunked
This medium-severity Red Hat Linux advisory covers CVE-2026-66338 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
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Summary
A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters.
When libsoup operates behind a strict frontend proxy, this parsing differential can be exploited to smuggle HTTP requests. The practical impact is limited because libsoup servers are rarely deployed in internet-facing infrastructure behind reverse proxies.
This issue is distinct from CVE-2026-1801 which covers bare LF tolerance. Red Hat severity: Low — CVSS 5.4 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N).
Weakness: CWE-444. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: libsoup3.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · medium-confidence parse· fetched 5 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 5 days ago·verify at source
Mitigation
The source record does not include mitigation steps. That does not mean no fix exists. Read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 5 days ago·verify at source
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