CVE-2026-55603: chimurai http-proxy-middleware · CRLF Injection
Affects chimurai http-proxy-middlewareSource CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to 4.1.1 or 3.0.7 soon.
Data as of 5 Nov 2026, 00:01 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 4.1.1, 3.0.7
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 22 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.
What to do
Upgrade chimurai http-proxy-middleware to 4.1.1 or 3.0.7.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| chimuraihttp-proxy-middleware | Affected
| Fixed in
|
| chimuraihttp-proxy-middleware | Affected
| Fixed in
|
npmhttp-proxy-middlewarepkg:npm/http-proxy-middlewareOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Upgrade http-proxy-middleware to version 3.0.7 or later, or 4.1.1 or later, where this vulnerability is fixed. Patch status is not explicitly stated but the description confirms the vulnerability is fixed starting at these versions. Until upgraded, avoid using the fixRequestBody() helper with multipart/form-data content types or apply custom input validation to neutralize CRLF sequences in request keys and values.
Description
http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Content-Type is multipart/form-data, it rebuilds the body with handlerFormDataBodyData(), which interpolates each req.body key and value directly into the multipart wire format without neutralizing CR/LF. A \r\n inside a value (or key) lets an attacker close the current part and inject an entirely new form part. Because the proxy's own body parser saw a single opaque value, any gateway-side policy or validation performed on req.body is evaluated against a different set of fields than the upstream backend ultimately parses a request/parameter desynchronization across the trust boundary. This vulnerability is fixed in 3.0.7 and 4.1.1.