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NVD / CVE Program· CNA GitHub_M

CVE-2026-55599: phpseclib: X.509 certificate validation sends attacker-controlled outbound requests (server-side request forgery) via Authority Information Access

Noroxi assessment

Priority: Monitor (action score 23/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.21% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: phpseclib phpseclib 1.0.30.

Low priority for now. Upgrade to phpseclib phpseclib 1.0.30 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

phpseclib is a PHP secure communications library. From 0.1.1 until 1.0.30, 2.0.55, and 3.0.54, when an application validates an untrusted X.509 certificate with phpseclib, X509::validateSignature() reads a URL out of that certificate's Authority Information Access (AIA) extension and connects to it. Attacker who supplies certificate fully controls host, port, and path of that connection. URL fetching is enabled by default, and no destination is blocked. An unauthenticated attacker can therefore make a validating server open connections to internal hosts and ports it should never reach, for example loopback 127.0.0.1, cloud metadata address 169.254.169.254, and internal-only services. This is a server-side request forgery (SSRF) caused by an insecure default. This vulnerability is fixed in 1.0.30, 2.0.55, and 3.0.54.

MediumCVSS 5.8 · v3.1—No exploit Fix available
Published
Jun 22, 2026
Updated
Jun 26, 2026
EPSS
0.2% · 11th percentile

Report tools

JSON

Action score

23

Monitor

Low priority for now.

CVSS
23 / 40 · 5.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
5.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
phpseclibphpseclib

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • phpseclib phpseclib0.1.1 and later · before 1.0.30
  • phpseclib phpseclib2.0.0 and later · before 2.0.55
  • phpseclib phpseclib3.0.0 and later · before 3.0.54

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • phpseclib phpseclib

    • >= 0.1.1, < 1.0.30, >= 2.0.0, < 2.0.55, >= 3.0.0, < 3.0.54affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12php-phpseclibfrom 0—
Debian:12php-phpseclib3from 0—
Debian:12phpseclibfrom 0—
Debian:14php-phpseclibbefore 2.0.55-12.0.55-1
Debian:14php-phpseclib3before 3.0.55-13.0.55-1
Packagistphpseclib/phpseclibfrom 0.1.1 · before 1.0.301.0.30
Packagistphpseclib/phpseclibfrom 2.0.0 · before 2.0.552.0.55
Packagistphpseclib/phpseclibfrom 3.0.0 · before 3.0.543.0.54

Same product

phpseclib: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-32935phpseclib's AES-CBC unpadding susceptible to padding oracle timing attack
    32Monitor
  • CVE-2026-44167phpseclib: CVE-2024-27355 mitigation bypass — OID amplification DoS in ASN1::decodeOID()
    30Monitor
  • CVE-2023-52892In phpseclib before 1.0.22, 2.x before 2.0.46, and 3.x before 3.0.33, some characters in Subject Alternative Name fields in TLS certificates
    30Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2024-27355Mar 1, 2024 · An issue was discovered in phpseclib 1.x before 1.0.23, 2.x before 2.0.47, and 3.x before 3.0.36.
    30Monitor
  • ← EarlierCVE-2026-40194Apr 10, 2026 · phpseclib has a variable-time HMAC comparison in SSH2::get_binary_packet() using != instead of hash_equals()
    14Monitor
  • Later →CVE-2026-84308Sep 1, 2026 · phpseclib — non-constant-time X25519 scalar multiplication permits full private-key recovery
    25Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
phpseclib phpseclib1.0.30 · descriptionVendor (CNA)
debian:php-phpseclib2.0.55-1 · Debian:14Package registry (OSV)
debian:php-phpseclib33.0.55-1 · Debian:14Package registry (OSV)
Packagist:phpseclib/phpseclib1.0.30Package registry (OSV)
Packagist:phpseclib/phpseclib2.0.55Package registry (OSV)
Packagist:phpseclib/phpseclib3.0.54Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
none
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

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

Weakness class (CWE)

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

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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