CVE-2026-66338
Low
No strong exploitation signal.
CVSS base
5.4
MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
EPSS — probability of exploitation (30 days)
0.2%
9.0th percentile
CISA KEV
Not listed
Weakness / dates
CWE-444
Published 2026-07-24 · modified 2026-08-24
CVSS breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
| Attack Vector | N | Network |
| Attack Complexity | H | High |
| Privileges Required | N | None |
| User Interaction | N | None |
| Scope | C | Changed |
| Confidentiality | L | Low |
| Integrity | L | Low |
| Availability | N | None |
Timeline
- 2026-07-24 — Published (NVD)
- 2026-08-24 — Last modified (NVD)
Description
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.