Summary
Permissive List of Allowed Inputs in ewe
ewe's chunked transfer encoding trailer handling merges declared trailer fields into req.headers after body parsing, but the denylist only blocks 9 header names. Security-sensitive headers like authorization, cookie, and x-forwarded-for can be injected or overwritten by a malicious client via trailers, potentially bypassing authentication or spoofing proxy-trust headers.
Proof of Concept
Inject an authorization header that didn't exist:
printf 'POST / HTTP/1.1\r\nHost: localhost:8080\r\nTransfer-Encoding: chunked\r\nTrailer: authorization\r\n\r\n4\r\ntest\r\n0\r\nauthorization: Bearer injected-token\r\n\r\n' | nc -w 2 localhost 8080
Overwrite a legitimate authorization header set by a proxy:
printf 'POST / HTTP/1.1\r\nHost: localhost:8080\r\nAuthorization: Bearer legitimate-token\r\nTransfer-Encoding: chunked\r\nTrailer: authorization\r\n\r\n4\r\ntest\r\n0\r\nauthorization: Bearer evil-token\r\n\r\n' | nc -w 2 localhost 8080
Inject x-forwarded-for to spoof client IP:
printf 'POST / HTTP/1.1\r\nHost: localhost:8080\r\nTransfer-Encoding: chunked\r\nTrailer: x-forwarded-for\r\n\r\n4\r\ntest\r\n0\r\nx-forwarded-for: 10.0.0.1\r\n\r\n' | nc -w 2 localhost 8080
Impact
When ewe.read_body processes a chunked request with a Trailer header, it calls handle_trailers (ewe/internal/http1.gleam:493), which merges declared trailer fields into req.headers via request.set_header (line 517). The is_forbidden_trailer denylist (line 534) only blocks 9 header names: transfer-encoding, content-length, host, cache-control, expect, max-forwards, pragma, range, and te.
Security-sensitive headers are not blocked, including:
authorization, attacker can inject or overwrite Bearer tokenscookie/set-cookie, attacker can inject session cookiesproxy-authorization, attacker can inject proxy credentialsx-forwarded-for,x-forwarded-host,x-forwarded-proto, attacker can spoof proxy-trust headersx-real-ip, attacker can spoof client IP
A malicious client can inject these headers by declaring them in the Trailer request header and including them after the final 0\r\n chunk. If the header already exists (e.g., set by a reverse proxy), request.set_header overwrites it. Any application logic that reads these headers after calling ewe.read_body, such as authentication middleware, IP-based rate limiting, or session validation, will see the attacker-controlled values.
CVE-2026-32881 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.0.5); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
- Expand the denylist in
is_forbidden_trailerto includeauthorization,cookie,set-cookie,proxy-authorization,x-forwarded-for,x-forwarded-host,x-forwarded-proto,x-real-ip, and other security-sensitive headers. - Alternatively, switch to an allowlist model that only permits explicitly safe trailer field names.
Frequently Asked Questions
- What is CVE-2026-32881? CVE-2026-32881 is a medium-severity security vulnerability in ewe (erlang), affecting versions >= 0.6.0, < 3.0.5. It is fixed in 3.0.5.
- How severe is CVE-2026-32881? CVE-2026-32881 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of ewe are affected by CVE-2026-32881? ewe (erlang) versions >= 0.6.0, < 3.0.5 is affected.
- Is there a fix for CVE-2026-32881? Yes. CVE-2026-32881 is fixed in 3.0.5. Upgrade to this version or later.
- Is CVE-2026-32881 exploitable, and should I be worried? Whether CVE-2026-32881 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-32881 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-32881? Upgrade
eweto 3.0.5 or later.