CVE Intelligence
Medium SSRF

CVE-2026-48998 — guzzlehttp/psr7 has Host Confusion via Authority Reinterpretation

guzzlehttp/psr7 is a PSR-7 HTTP message library implementation in PHP. Versions prior to 2.10.2 contain improper Host header validation when parsing raw HTTP request messages and when deriving a server request URI from server variables. An attacker can provide a malformed Host header containing URI authority delimiters, such as `trusted.example@evil.example`. When the Host value is used to construct a URI, the malformed value can be reinterpreted as URI userinfo and host. This can cause the PSR-7 request URI host to differ from the original Host header value. Applications are affected if they parse attacker-controlled raw HTTP requests with `GuzzleHttp\Psr7\Message::parseRequest()` or the legacy 1.x `GuzzleHttp\Psr7\parse_request()` function, or if they build server requests from attacker-controlled server variables, then rely on the resulting URI host for routing, allow-list checks, or forwarding decisions. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host. The issue is patched in `2.10.2`. `1.x` is end-of-life and will not receive a patch. Some workarounds are available. Validate the `Host` header as `uri-host [ ":" port ]` before calling `Message::parseRequest()` or legacy `parse_request()` on untrusted HTTP request data, or before deriving routing and forwarding decisions from a parsed request URI. Reject Host values containing userinfo, path, query, or fragment delimiters.

Published Jun 11, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.3% (30-day exploitation probability)+3
  • Technical severity (medium)+3
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.31%
ahead of 23% of scored CVEs · Oct 14, 2026
Affects
Guzzle
Psr7 and 1 more
CVSS base
5.3
Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented mitigation — github.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Guzzle Psr7, Guzzlephp Psr-7).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the documented mitigations until a definitive fix is available.
  4. Search available logs for exploit probes matching the vulnerability class (ssrf), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Guzzle Psr7 version < 2.10.2 Vulnerable CVE Program (cve.org) e CISA ADP
Guzzlephp Psr-7 < 2.10.2 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
5.3 CVSS 3.1 Medium 3.9 1.4 security-advisories@github.com via NIST National Vulnerability Database
5.3 CVSS 3.1 Medium — — GitHub_M via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-918 · Server-Side Request Forgery (SSRF)

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.31%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Monitor outbound requests from the server to internal IPs and cloud metadata endpoints.
web/proxy/WAF logsnetwork IDS/IPSegress traffic

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · guzzle/psr7
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 5.3
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Jun 11, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

Elsewhere on this site

Guzzle
every CVE for this vendor
SSRF
same class
CWE-918
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-59882 guzzlehttp/psr7: Host Confusion via Weak URI Host Validation Jul 8, 2026
  • CVE-2026-55766 guzzlehttp/psr7: CRLF Injection in HTTP Start-Line Serialization Jun 23, 2026
  • CVE-2026-49214 guzzlehttp/psr7 has CRLF Injection via URI Host Component Jun 11, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-48998 is "guzzlehttp/psr7 has Host Confusion via Authority Reinterpretation", rated Medium. It affects Psr7 (Guzzle); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.3 describes technical severity. EPSS 0.31% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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