CVE-2026-55766
is CVE-2026-55766real, exploitable, or a false positive? Here's the community verdict.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
guzzlehttp/psr7 is a PSR-7 HTTP message library implementation in PHP. Prior to 2.12.1, guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again. Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This vulnerability is fixed in 2.12.1.
References
Published
Embed this verdict
[](https://www.truepositive.app/cve/CVE-2026-55766)<a href="https://www.truepositive.app/cve/CVE-2026-55766"><img src="https://www.truepositive.app/cve/CVE-2026-55766/badge.svg" alt="TruePositive verdict for CVE-2026-55766"></a>Live badge that updates automatically as the community verdict changes.
Community ground truth
In your experience, is this finding real and exploitable?
0 verdictsNo account needed. Anonymous verdicts post as an unverified signal. Log in to make yours verified and earn reputation.
Field notes & remediation
Verdicts are the quick signal. Notes are the evidence and fixes behind them.
No notes yet. Be the first to share what you saw, or a fix that worked.
Add a field note or remediationoptional
Related CVEs
Same weakness: CWE-93.
- CVE-2026-50639CVSS 6.5EPSS 0%
Metrics::Any::Adapter::SignalFx versions before 0.04 for Perl does not protect against metric injections. The statsd protocol (and extensions such as dogstatsd) allow mutiple metrics, separated by newlines, to be sent per packet. Metrics::Any::Adapter::SignalFx which extends Metrics::Any::Adapter::Statsd, which has a similar vulnerability. In addition, the _labels function does not check tags labels newlines or statsd control characters. The labels can be used for metric injections.
- CVE-2026-55603CVSS 7.5EPSS 0%
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.