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Response snapshot Oct 31, 2026, 00:16 UTC

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VulnerabilityCVE-2026-63182

LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings.

LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. Prior to 4.7.1 and 5.0.1, LightSAML and xmlseclibs disagree about which assertion an inbound SAML signature covers.

At a glance

Exploited
Not known
Severity
8.1 High (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

Check the vendor advisory for affected versions and fixes.

Read NVD CVE-2026-63182 (opens a new tab)

What happened

LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. Prior to 4.7.1 and 5.0.1, LightSAML and xmlseclibs disagree about which assertion an inbound SAML signature covers.

Response::deserialize uses manyElementsFromXml to collect only direct-child saml:Assertion elements of samlp:Response, and AssertionSignatureValidatorAction validates their ds:Signature using an out-of-band trusted IdP credential resolved by Issuer, not a key from the document.

XMLSecurityDSig::validateReference() removes the enveloped signature from the shared DOM, but processRefNode() resolves Reference URI="#id" document-wide through an XPath of the form //*[@Id] and takes item(0), which need not be the assertion whose claims LightSAML consumes.

An attacker who has captured one genuinely signed assertion, such as an earlier login response, can place its signature-stripped bytes earlier in samlp:Extensions and present a forged direct-child assertion with the same ID and copied genuine signature.

Continue reading

Validation then covers the hidden genuine bytes while LightSAML surfaces unsigned attacker-controlled Subject/NameID, Conditions, and Attributes, enabling authentication bypass or privilege escalation even when signature validation is required. The behavior was confirmed in versions 5.0.0 and 4.6.1. This issue is fixed in versions 4.7.1 and 5.0.1.

Scores and how they were measured

CVSS base severity

8.1

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Sources

  1. Primary source

    NVD CVE-2026-63182 (opens a new tab)

    NVD record: description, CVSS (the CNA score is preferred), affected products, and publication date. Not evidence of exploitation.

    Published Checked

  2. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  3. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

  4. Primary source

    NVD CVE API 2.0 (opens a new tab)

    The NVD API page that supplied this CVE record.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 30). LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. (CVE-2026-63182). https://kevwire.com/record/CVE-2026-63182

MLA

"LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. (CVE-2026-63182)." KEVWire, 30 Oct. 2026, kevwire.com/record/CVE-2026-63182.

Chicago

KEVWire. "LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. (CVE-2026-63182)." Last modified October 30, 2026. https://kevwire.com/record/CVE-2026-63182.

Evidence summary (plain text)

LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. (Oct 30, 2026).
LightSAML implements SAML 2.0 data model classes, XML serialization and deserialization, XML security, certificate support, and message bindings. Prior to 4.7.1 and 5.0.1, LightSAML and xmlseclibs disagree about which assertion an inbound SAML signature covers. Response::deserialize uses manyElementsFromXml to collect only direct-child saml:Assertion elements of samlp:Response, and AssertionSignatureValidatorAction validates their ds:Signature using an out-of-band trusted IdP credential resolved by Issuer, not a key from the document.
CVSS 8.1 (version 3.1; evidence as of Oct 30, 2026; https://nvd.nist.gov/vuln/detail/CVE-2026-63182).
Sources:
NVD CVE-2026-63182: https://nvd.nist.gov/vuln/detail/CVE-2026-63182
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T22:05:59.313Z&lastModEndDate=2026-10-30T23:40:58.124Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T21:30:58.248Z&lastModEndDate=2026-10-30T23:05:57.023Z&resultsPerPage=500&startIndex=0
NVD CVE API 2.0: https://services.nvd.nist.gov/rest/json/cves/2.0?lastModStartDate=2026-10-30T20:56:01.746Z&lastModEndDate=2026-10-30T22:30:56.395Z&resultsPerPage=500&startIndex=0
Record ID: CVE-2026-63182.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 30, 2026, 23:40 UTC. Ingestion is not an independent editorial investigation.

NVD status: Received. Publication in the NVD is not evidence of exploitation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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Record details

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