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.

The remote Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-2aa96a9ce5 advisory.

    ## Release 1.7.3

    - OAuth: Don't log an error when a refreshed token's TTL is below refresh_interval (#10213)
    - Fix out-of-bounds string reads on truncated compressed-RTF in the TNEF decoder (#10269)
    - Fix bug where searching in example_addressbook plugin was reporting zero results despite matches (#9022)
    - Fix vCard import mis-detecting folded continuation lines as BEGIN/END:VCARD (#9593)
    - Fix bug where the php session driver practically disabled session.lazy_write optimization (#9885,     #10248)
    - Fix bug where dates could get displayed shifted back one day in some places (#9403)
    - Fix regression where it wasn't possible to hide a skin logo image anymore (#10254)
    - Fix decoding of multi-segment RFC2231 extended attachment filenames (#10268)
    - Fix vCard import silently dropping properties with a non-item group prefix (#10271)
    - Fix so `REQUEST_URI` is used as a fallback if `PATH_INFO` is empty in static.php (#10181)
    - Security: Add basic validation for content proxied by the css proxy
    - Security: Fix SSRF bypass via specific local address URLs using 100.64.0.0/10 and fe80::/10 nets
    - Security: Fix SSRF filter bypass via various forms of nip.io/sslip.io hostnames evading is_local_url()     check
    - Security: Fix remote content blocking bypass via unclosed url() in a FuncIRI attribute
    - Security: Fix LDAP filter injection via unescaped %u/%fu/%d substitution into the `search_filter`
    - Security: Fix arbitrary Sieve script injection via a filter rule name bypassing     `managesieve_disabled_actions`
    - Security: Fix RCE via `cmd_learn` driver of markasjunk plugin
    - Security: Fix IMAP command injection via mail search and LITERAL+ byte-count desynchronization
    - Security: Fix password's modoboa driver leak of an authentication token to a user-controlled host
    - Security: Fix stored XSS in Add to address book action
    - Security: Fix HTML/CSS sanitization bypass via SVG animate `by` attribute



Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-914a40b4fd advisory.


    ## Release 1.6.18

    - Password: Fix fatal error Class 'Zxcvbn' not found (#10274)
    - Fix out-of-bounds string reads on truncated compressed-RTF in the TNEF decoder (#10269)
    - Security: Add basic validation for content proxied by the css proxy
    - Security: Fix SSRF bypass via specific local address URLs using 100.64.0.0/10 and fe80::/10 nets
    - Security: Fix SSRF filter bypass via various forms of nip.io/sslip.io hostnames evading is_local_url()     check
    - Security: Fix remote content blocking bypass via unclosed url() in a FuncIRI attribute
    - Security: Fix LDAP filter injection via unescaped %u/%fu/%d substitution into the `search_filter`
    - Security: Fix arbitrary Sieve script injection via a filter rule name bypassing     `managesieve_disabled_actions`
    - Security: Fix RCE via `cmd_learn` driver of markasjunk plugin
    - Security: Fix IMAP command injection via mail search and LITERAL+ byte-count desynchronization
    - Security: Fix password's modoboa driver leak of an authentication token to a user-controlled host
    - Security: Fix stored XSS in Add to address book action
    - Security: Fix HTML/CSS sanitization bypass via SVG animate `by` attribute



Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-ee50c21f92 advisory.

    33.0.6 Release

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-5afe6630dc advisory.

    33.0.6 Release

Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-55766)

Note that Nessus relies on the presence of the package as reported by the vendor.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - 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. (CVE-2026-55766)

ID	Name	Product	Family	Type	Severity
338391	Fedora 44 : roundcubemail (2026-2aa96a9ce5)	Nessus	Fedora Local Security Checks	Local	medium
338387	Fedora 43 : roundcubemail (2026-914a40b4fd)	Nessus	Fedora Local Security Checks	Local	medium
325136	Fedora 44 : nextcloud (2026-ee50c21f92)	Nessus	Fedora Local Security Checks	Local	high
325111	Fedora 43 : nextcloud (2026-5afe6630dc)	Nessus	Fedora Local Security Checks	Local	high
321774	Linux Distros Unpatched Vulnerability : CVE-2026-55766	Nessus	Misc.	Local	medium
443586	SCA: security update for guzzlehttp/psr7 (GHSA-vm85-hxw5-5432)	Tenable Cloud Security	SCA Checks	Local	medium
443586	SCA: security update for guzzlehttp/psr7 (GHSA-vm85-hxw5-5432)	Tenable Self-Hosted Container Security	SCA Checks	Local	medium

Detections

Analytics

CVE-2026-55766

medium

Tenable Plugins

medium

medium

high

high

medium

medium

medium