Critical technical impact with a remotely reachable, unauthenticated path and a public exploit reference; no CISA KEV confirmation is currently recorded.
Patch available
Distribution package intelligence
Ubuntu vendor package status
Canonical’s release and source-package findings are shown separately from local repository availability.
1 package state
Repository candidate not checked
A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.
Ubuntu release
Source package
Vendor state
Fixed version
Evidence
Ubuntu 24.04 LTSnoble · esm-apps
python-authlib
Vendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.
Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.
1 current
CVE-2026-27962 · CSAF 2.0 · revision 3 · finalRed Hat Product Securityauthlib: Authlib: Authentication bypass due to JWK Header Injection vulnerability
18 fixed
The vendor explicitly identifies these products or versions as containing the fix.
registry.redhat.io/quay/quay-rhel8@sha256:6e13793ca8f309ec0b69ae609b840ff0f41989d88cd4bba127e1b0040631367e_ppc64le as a component of Red Hat Quay 3.10
registry.redhat.io/quay/quay-rhel8@sha256:c0d00643c4ac6f84e5327192a29c6353b5dcac34d483d0a3e5f39d366127fcc2_amd64 as a component of Red Hat Quay 3.10
registry.redhat.io/quay/quay-rhel8@sha256:f6a231ebb14c74e194a8091822fe6a981e1cec92d223e04e6d0f12b60206259a_s390x as a component of Red Hat Quay 3.10
registry.redhat.io/quay/quay-rhel8@sha256:01f890a5280ddd4093134dc21578f8a5f06cdade4b9a6d59f31ca8deec8c43c3_arm64 as a component of Red Hat Quay 3.14
registry.redhat.io/quay/quay-rhel8@sha256:3f44613559972c360a7e0cfce386ee3d840bc36dcb16175780835d53babe482f_amd64 as a component of Red Hat Quay 3.14
registry.redhat.io/quay/quay-rhel8@sha256:5e1a86fac8d2a2a63daccd105780c5a526e26d051ffdd62d4f64c3da6561011b_ppc64le as a component of Red Hat Quay 3.14
registry.redhat.io/quay/quay-rhel8@sha256:cfc2d2a2638d28ec365e50ddf997dd0fcc8782987ab5987db729e55b8f2c53e5_s390x as a component of Red Hat Quay 3.14
registry.redhat.io/quay/quay-rhel8@sha256:5b1b98cd31ba150aecd6ef44c2bd8d79ae64380c8e974a4c8c1bb66fb4a38ce9_ppc64le as a component of Red Hat Quay 3.15
registry.redhat.io/quay/quay-rhel8@sha256:88ca55bb3177d8111971f1ba134bec7967289bfae64ecdf0b751dba0df82d9f0_s390x as a component of Red Hat Quay 3.15
registry.redhat.io/quay/quay-rhel8@sha256:afeeca0c1a653b5c375af4cca8dac1f52db846013d8b50e914ed62e1b7b1aa62_amd64 as a component of Red Hat Quay 3.15
registry.redhat.io/quay/quay-rhel9@sha256:139cae64e4790ebf8b760c6376a33d15233222a25e4da39c6062d7e46c3a1bef_amd64 as a component of Red Hat Quay 3.16
registry.redhat.io/quay/quay-rhel9@sha256:52883f389182907dec0e286d626c4faea0f4ae29a5d0e841d6ad2287fdb964c2_arm64 as a component of Red Hat Quay 3.16
Summary
A flaw was found in Authlib, a Python library used for creating secure authentication and authorization systems. This vulnerability, known as JWK (JSON Web Key) Header Injection, affects how Authlib verifies digital signatures in JWS (JSON Web Signature) tokens. An attacker can exploit this by creating a specially crafted token that includes their own cryptographic key in the header. When the system attempts to verify this token without a predefined key, it mistakenly uses the attacker's key, allowing them to bypass authentication and gain unauthorized access.
Remediation
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Optional official sources
National CERT insights ?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.
Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.
Official European source
ENISA European Vulnerability Database
Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.
1 current
ENISA EUVD identifier
EUVD-2026-12478
No EUVD known-exploited evidence
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.
EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
9.1 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 72 hours
Critical technical impact with a remotely reachable, unauthenticated path and a public exploit reference; no CISA KEV confirmation is currently recorded.
Patch available
01
What, why and how
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.
What
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.
Why
The product does not verify, or incorrectly verifies, the cryptographic signature for data.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.
Why
The product does not verify, or incorrectly verifies, the cryptographic signature for data.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation ?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No confirmed evidence
No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material ?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.Reference recorded
A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.
Likely attack path
a network path → Improper Verification of Cryptographic Signature → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness ?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-347: Improper Verification of Cryptographic Signature. The product does not verify, or incorrectly verifies, the cryptographic signature for data.
CVSS vector ?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
Only matched European and national findings are included. Language selectors and unavailable sources are omitted.
ENISA EUVD · EUVD-2026-12478Official EUVD mapping
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a JWK Header Injection vulnerability in authlib's JWS implementation allows an unauthenticated attacker to forge arbitrary JWT tokens that pass signature verification. When key=None is passed to any JWS deserialization function, the library extracts and uses the cryptographic key embedded in the attacker-controlled JWT jwk header field. An attacker can sign a token with their own private key, embed the matching public key in the header, and have the server accept the forged token as cryptographically valid — bypassing authentication and authorization entirely. This issue has been patched in version 1.6.9.
Official EUVD record ↗Cyber Security Agency of Singapore · English · CSA-SB-20260318Security Bulletin 18 Mar 2026
The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 18 Mar 2026, published on 18 March 2026. Open the linked bulletin for the product, severity and reference information published in that issue.
Official advisory ↗JVN iPedia · Japanese · JVNDB-2026-007825authlibにおけるデジタル署名の検証に関する脆弱性
Operational remediation based on structured source evidence.
Status ?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Before applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
Workaround
A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04
Evidence and provenance
Published 16 Mar 2026 · Last source change 24 Aug 2026, 12:06 UTC · CWE-347 · Improper Verification of Cryptographic Signature
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source ?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-12478
Product sourceCNA
Remediation sourceVendor CSAF · Red Hat Product Security
CWE sourceCNA
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Affected versionsThe structured affected or fixed version information changed.
Before
< 1.6.9 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
After
authlib: < 1.6.9 · Fixed: RHSA-2026:7314: Red Hat Quay 3.14
Affected versionsThe structured affected or fixed version information changed.
Before
Fixed: registry.redhat.io/quay/quay-rhel8@sha256:01f890a5280ddd4093134dc21578f8a5f06cdade4b9a6d59f31ca8deec8c43c3_arm64 as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:3f44613559972c360a7e0cfce386ee3d840bc36dcb16175780835d53babe482f_amd64 as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:5e1a86fac8d2a2a63daccd105780c5a526e26d051ffdd62d4f64c3da6561011b_ppc64le as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:cfc2d2a2638d28ec365e50ddf997dd0fcc8782987ab5987db729e55b8f2c53e5_s390x as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:5b1b98cd31ba150aecd6ef44c2bd8d79ae64380c8e974a4c8c1bb66fb4a38ce9_ppc64le as a component of Red Hat Quay 3.15; registry.redhat.io/quay/quay-rhel8@sha256:88ca55bb3177d8111971f1ba134bec7967289bfae64ecdf0b751dba0df82d9f0_s390x as a component of Red Hat Quay 3.15; registry.redhat.io/quay/quay-rhel8@sha256:afeeca0c1a653b5c375af4cca8dac1f52db846013d8b50e914ed62e1b7b1aa62_amd64 as a component of Red Hat Quay 3.15; registry.redhat.io/quay/quay-rhel9@sha256:139cae64e4790ebf8b760c6376a33d15233222a25e4da39c6062d7e46c3a1bef_amd64 as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:52883f389182907dec0e286d626c4faea0f4ae29a5d0e841d6ad2287fdb964c2_arm64 as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:ad162e6ea2f6fd246f605180699ce36e4ea91c4b551c7af600a64e671a303ee9_s390x as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:f6a15c2f1b4d5900cdbd366080e40d3a90d51ba9e5b4d6196e15eefe69d902c3_ppc64le as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:14e7fd727c1dc74e19001952176a8354cbc97ec5b4643a4815b6ffbc6d76e224_s390x as a component of Red Hat Quay 3.18; registry.redhat.io/quay/quay-rhel9@sha256:4207ba218f8ae31531add66d3ef5bf726f0034dfa7abb109d2c1bb1e2ed8b95b_ppc64le as a component of Red Hat Quay 3.18; registry.redhat.io/quay/quay-rhel9@sha256:6446f4989c8ad3d09abbd7ccf4af8ee341044f833b2d1e8d2c410c899dc1aa80_amd64 as a component of Red Hat Quay 3.18; registry.redhat.io/quay/quay-rhel9@sha256:9ee2985651443aef099fd421de5e9b7adb550aeafe2479a424864b85e0e50bc1_arm64 as a component of Red Hat Quay 3.18; registry.redhat.io/quay/quay-rhel8@sha256:6e13793ca8f309ec0b69ae609b840ff0f41989d88cd4bba127e1b0040631367e_ppc64le as a component of Red Hat Quay 3.1; registry.redhat.io/quay/quay-rhel8@sha256:c0d00643c4ac6f84e5327192a29c6353b5dcac34d483d0a3e5f39d366127fcc2_amd64 as a component of Red Hat Quay 3.1; registry.redhat.io/quay/quay-rhel8@sha256:f6a231ebb14c74e194a8091822fe6a981e1cec92d223e04e6d0f12b60206259a_s390x as a component of Red Hat Quay 3.1
After
Fixed: registry.redhat.io/quay/quay-rhel8@sha256:6e13793ca8f309ec0b69ae609b840ff0f41989d88cd4bba127e1b0040631367e_ppc64le as a component of Red Hat Quay 3.10; registry.redhat.io/quay/quay-rhel8@sha256:c0d00643c4ac6f84e5327192a29c6353b5dcac34d483d0a3e5f39d366127fcc2_amd64 as a component of Red Hat Quay 3.10; registry.redhat.io/quay/quay-rhel8@sha256:f6a231ebb14c74e194a8091822fe6a981e1cec92d223e04e6d0f12b60206259a_s390x as a component of Red Hat Quay 3.10; registry.redhat.io/quay/quay-rhel8@sha256:01f890a5280ddd4093134dc21578f8a5f06cdade4b9a6d59f31ca8deec8c43c3_arm64 as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:3f44613559972c360a7e0cfce386ee3d840bc36dcb16175780835d53babe482f_amd64 as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:5e1a86fac8d2a2a63daccd105780c5a526e26d051ffdd62d4f64c3da6561011b_ppc64le as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:cfc2d2a2638d28ec365e50ddf997dd0fcc8782987ab5987db729e55b8f2c53e5_s390x as a component of Red Hat Quay 3.14; registry.redhat.io/quay/quay-rhel8@sha256:5b1b98cd31ba150aecd6ef44c2bd8d79ae64380c8e974a4c8c1bb66fb4a38ce9_ppc64le as a component of Red Hat Quay 3.15; registry.redhat.io/quay/quay-rhel8@sha256:88ca55bb3177d8111971f1ba134bec7967289bfae64ecdf0b751dba0df82d9f0_s390x as a component of Red Hat Quay 3.15; registry.redhat.io/quay/quay-rhel8@sha256:afeeca0c1a653b5c375af4cca8dac1f52db846013d8b50e914ed62e1b7b1aa62_amd64 as a component of Red Hat Quay 3.15; registry.redhat.io/quay/quay-rhel9@sha256:139cae64e4790ebf8b760c6376a33d15233222a25e4da39c6062d7e46c3a1bef_amd64 as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:52883f389182907dec0e286d626c4faea0f4ae29a5d0e841d6ad2287fdb964c2_arm64 as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:ad162e6ea2f6fd246f605180699ce36e4ea91c4b551c7af600a64e671a303ee9_s390x as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:f6a15c2f1b4d5900cdbd366080e40d3a90d51ba9e5b4d6196e15eefe69d902c3_ppc64le as a component of Red Hat Quay 3.16; registry.redhat.io/quay/quay-rhel9@sha256:14e7fd727c1dc74e19001952176a8354cbc97ec5b4643a4815b6ffbc6d76e224_s390x as a component of Red Hat Quay 3.18; registry.redhat.io/quay/quay-rhel9@sha256:4207ba218f8ae31531add66d3ef5bf726f0034dfa7abb109d2c1bb1e2ed8b95b_ppc64le as a component of Red Hat Quay 3.18; registry.redhat.io/quay/quay-rhel9@sha256:6446f4989c8ad3d09abbd7ccf4af8ee341044f833b2d1e8d2c410c899dc1aa80_amd64 as a component of Red Hat Quay 3.18; registry.redhat.io/quay/quay-rhel9@sha256:9ee2985651443aef099fd421de5e9b7adb550aeafe2479a424864b85e0e50bc1_arm64 as a component of Red Hat Quay 3.18
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
