php-guzzlehttp-psr7 — security advisory
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.
- Products
- php-guzzlehttp-psr7
- Affected versions
- 2.10.3-1, 2.10.4-1, 2.11.0-1, 2.12.0-1, 2.12.1-1, 2.12.3-1, 2.12.4-1, 2.12.5-1, 2.13.0-1, 2.13.1-1, 2.4.5-1, 2.4.5-1+deb12u1, 2.5.0-1, 2.6.0-1, 2.6.1-1, 2.6.2-1, 2.6.2-2, 2.6.2-3, 2.7.0-1, 2.7.0-2, 2.7.0-3, 2.7.1-1, 2.7.1-1+deb13u1, 2.8.0-1, 2.8.0-2, 2.9.0-1, 2.9.0-2, 3.0.0-1, 3.1.0-1, 3.2.0-1
- Fixed versions
- 2.12.1-1, 2.7.1-1+deb13u2
- CVEs
- CVE-2026-55766
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 12:31 UTC · Revision 2
Source evidence
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.
osv:DEBIAN-CVE-2026-55766
php-guzzlehttp-psr7
Fixed versions: Not specified
php-guzzlehttp-psr7
Fixed versions: 2.7.1-1+deb13u2
php-guzzlehttp-psr7
Fixed versions: 2.12.1-1
Complete source record
{
"id": "e2030cb948a2ea6706034840b703c82009cf1705c0845dff1f5fff59bbd04c34",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-55766",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-55766",
"summary": "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.",
"evidence": "osv:DEBIAN-CVE-2026-55766",
"products": [
{
"name": {
"value": "php-guzzlehttp-psr7",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
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"affected_versions": [
{
"value": "2.10.3-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.10.4-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.11.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.12.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.12.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.12.3-1",
"evidence": "/affected/0/versions"
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{
"value": "2.12.4-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.12.5-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.13.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.13.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.4.5-1",
"evidence": "/affected/0/versions"
},
{
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"evidence": "/affected/0/versions"
},
{
"value": "2.5.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.2-2",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.2-3",
"evidence": "/affected/0/versions"
},
{
"value": "2.7.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.7.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "2.7.0-3",
"evidence": "/affected/0/versions"
},
{
"value": "2.7.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.8.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.8.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "2.9.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.9.0-2",
"evidence": "/affected/0/versions"
},
{
"value": "3.0.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.1.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "3.2.0-1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "php-guzzlehttp-psr7",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "2.7.1-1+deb13u2",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": [
{
"value": "2.7.1-1",
"evidence": "/affected/1/versions"
},
{
"value": "2.7.1-1+deb13u1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "php-guzzlehttp-psr7",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "2.12.1-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "2.10.3-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.10.4-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.11.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.12.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.7.1-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.8.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.8.0-2",
"evidence": "/affected/2/versions"
},
{
"value": "2.9.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.9.0-2",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "DEBIAN-CVE-2026-55766",
"aliases": [
"DEBIAN-CVE-2026-55766"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "php-guzzlehttp-psr7",
"purl": "pkg:deb/debian/php-guzzlehttp-psr7?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"2.10.3-1",
"2.10.4-1",
"2.11.0-1",
"2.12.0-1",
"2.12.1-1",
"2.12.3-1",
"2.12.4-1",
"2.12.5-1",
"2.13.0-1",
"2.13.1-1",
"2.4.5-1",
"2.4.5-1+deb12u1",
"2.5.0-1",
"2.6.0-1",
"2.6.1-1",
"2.6.2-1",
"2.6.2-2",
"2.6.2-3",
"2.7.0-1",
"2.7.0-2",
"2.7.0-3",
"2.7.1-1",
"2.8.0-1",
"2.8.0-2",
"2.9.0-1",
"2.9.0-2",
"3.0.0-1",
"3.1.0-1",
"3.2.0-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55766.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.7.1-1+deb13u2"
}
]
}
],
"package": {
"name": "php-guzzlehttp-psr7",
"purl": "pkg:deb/debian/php-guzzlehttp-psr7?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"2.7.1-1",
"2.7.1-1+deb13u1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55766.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.12.1-1"
}
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}
],
"package": {
"name": "php-guzzlehttp-psr7",
"purl": "pkg:deb/debian/php-guzzlehttp-psr7?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"2.10.3-1",
"2.10.4-1",
"2.11.0-1",
"2.12.0-1",
"2.7.1-1",
"2.8.0-1",
"2.8.0-2",
"2.9.0-1",
"2.9.0-2"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-55766.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-26T12:00:46.084715992Z",
"provider": "osv",
"upstream": [
"CVE-2026-55766"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-55766"
]
},
"related_cves": [
{
"value": "CVE-2026-55766",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 451138,
"published_at": "2026-06-23T16:17:03.127+00:00"
}