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CVE-2026-66357

inets,httpd:HTTP Request Smuggling via obs-fold Header Continuation

HIGH
8.3
CVSS Score
Published: September 1, 2026 at 02:40 PM UTC
Updated: September 8, 2026 at 01:17 AM UTC
1 product affected across 1 vendorErlang /otp

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Severity
HIGH8.3
Exploit prediction
EPSS 0.6%
SSVC
No known exploit

Description

httpd has never implemented obs-fold (RFC 2616 §2.2 / RFC 7230 §3.2.4 header continuation lines). Every CRLF followed by a non-CRLF octet unconditionally starts a new header. This missing feature became a security concern as the understanding of HTTP request smuggling attacks evolved. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Erlang /otp· Erlang
95%
v < 27.3.4.1717.0 ≤ v < 27.3.4.1728.0 ≤ v < 28.5.0.629.0 ≤ v < 29.0.65.10 ≤ v < 9.3.2.79.4 ≤ v < 9.6.2.39.7 ≤ v < 9.7.217.028.029.05.1084adefa331c4159d432d22840663c38f155cd4c19.49.7
Affected range stops below 27.3.4.17, so it looks safe — our inference, not a vendor statement
Affected range stops below 28.5.0.6, so it looks safe — our inference, not a vendor statement
Affected range stops below 29.0.6, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.3.2.7, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.6.2.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 9.7.2, so it looks safe — our inference, not a vendor statement
Vendor states this is fixed in 17.0 (unknown)
Vendor states this is fixed in 5.10 (unknown)

References (6)

Vendor Advisory
Source: cverecord
https://github.com/erlang/otp/security/advisories/GHSA-qh2f-33hj-37qf
Related
Source: cverecord
https://cna.erlef.org/cves/CVE-2026-66357.html
Related
Source: cverecord
https://osv.dev/vulnerability/EEF-CVE-2026-66357
Patch
Source: cverecord
https://github.com/erlang/otp/commit/220d618d2479a7180b4a06d0c5aacfaa4af4a85b
Patch
Source: cverecord
https://github.com/erlang/otp/commit/273d8958de38ff2a7fe0c5dcc5b6bfe6f65717f3
Patch
Source: cverecord
https://github.com/erlang/otp/commit/e640d599287d2eba919e6f13b91f042d7dbe6ff4

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.3HIGHEEF
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-444

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