CVE-2026-23941: Request smuggling via first-wins Content-Length parsing in inets httpd
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.5%
EPSS score, percentile 40.6 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 7.0 High
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
- Which versions are affected?
Affected
- 5.10
- 17.0
Unaffected from 9.6.1; from 9.3.2.3; from 9.1.0.5; from 28.4.1; from 27.3.4.9; from 26.2.5.18
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Workaround (from the CVE record)
* Configure frontend proxy to reject requests with duplicate Content-Length headers. * Disable HTTP keep-alive on httpd by adding `{keep_alive, false}` to httpd configuration. Note: This impacts performance for clients making multiple requests. * Deploy a Web Application Firewall (WAF) configured to reject requests with multiple Content-Length headers.
Advisories and patches
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | 5.10 |
| Unaffected | from 9.6.1 |
| Unaffected | from 9.3.2.3 |
| Unaffected | from 9.1.0.5 |
Versions not listed are: unknown.
| Status | Versions |
|---|---|
| Affected | 17.0 |
| Unaffected | from 28.4.1 |
| Unaffected | from 27.3.4.9 |
| Unaffected | from 26.2.5.18 |
| Affected | 84adefa331c4 |
| Unaffected | from a4b46336fd25 |
| Unaffected | from a761d391d8d0 |
| Unaffected | from e775a332f623 |
Versions not listed are: unknown.
Versions the record lists as unaffected: 9.6.1, 9.3.2.3, 9.1.0.5, 28.4.1, 27.3.4.9, 26.2.5.18, a4b46336fd25aa100ac602eb9a627aaead7eda18, a761d391d8d08316cbd7d4a86733ba932b73c45b.
Source: CVE List, as of . About the data.
About this vulnerability
Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') vulnerability in Erlang OTP (inets httpd module) allows HTTP Request Smuggling. This vulnerability is associated with program files lib/inets/src/http_server/httpd_request.erl and program routines httpd_request:parse_headers/7. The server does not reject or normalize duplicate Content-Length headers. The earliest Content-Le…
Summary: CVE record, as of .
- CISA has not added CVE-2026-23941 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 13 Mar 2026.
- The CVE record carries a CVSS v4.0 base score of 7.0 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.5% (percentile 40.6), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
- The credits in the CVE record name AISLE as finder.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
Request smuggling via first-wins Content-Length parsing in inets httpd
Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling') vulnerability in Erlang OTP (inets httpd module) allows HTTP Request Smuggling. This vulnerability is associated with program files lib/inets/src/http_server/httpd_request.erl and program routines httpd_request:parse_headers/7. The server does not reject or normalize duplicate Content-Length headers. The earliest Content-Length in the request is used for body parsing while common reverse proxies (nginx, Apache httpd, Envoy) honor the last Content-Length value. This violates RFC 9112 Section 6.3 and allows front-end/back-end desynchronization, leaving attacker-controlled bytes queued as the start of the next request. This issue affects OTP from OTP 17.0 before OTP 28.4.1, OTP 27.3.4.9 and OTP 26.2.5.18, corresponding to inets from 5.10 before 9.6.1, 9.3.2.3 and 9.1.0.5.
Source: CVE List, as of . About the data.
Weakness
CWE-444, 1 CAPEC
- CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')
Attack patterns (CAPEC)
- CAPEC-33: HTTP Request Smuggling
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |
References
3
Known exploited Erlang vulnerabilities
- CVE-2025-32433: Erlang Erlang/OTP SSH Server Missing Authentication for Critical Function Vulnerability