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NVD / CVE Program· CNA GitHub_M

CVE-2026-62995: joserfc accepts JWT with padding, leading to JWT malleability

Noroxi assessment

Priority: Monitor (action score 9/100)

  • 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: 0.14% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. A low-privileged account is enough. 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: authlib joserfc 1.7.2.

Low priority for now. Upgrade to authlib joserfc 1.7.2 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

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. in versions 1.7.1 and prior, joserfc accepts JWTs with trailing padding (==) which are not conforming to the JOSE specifications. This leads to malleability of the JWTs when consumed by joserfc. Depending on this application this might or not be an issue. This could lead to bypass of token revocation or anti-replay protection when implemented as a deny list of tokens or a deny list of token hashes. Note that ECDSA JWS are always malleable because of the malleability of ECDSA signatures (first test case in the code bellow). This makes a scheme which assumes that JWTs are not malleable brittle. However for other signatures (or MAC) schemes it might make sense to assume non malleability of the token. This issue has been fixed in version 1.7.2.

LowCVSS 2.3 · v4.0—No exploit Fix available
Published
Jul 29, 2026
Updated
Oct 24, 2026
EPSS
0.1% · 3th percentile

Report tools

JSON

Action score

9

Monitor

Low priority for now.

CVSS
9 / 40 · 2.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
2.3
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

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

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

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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • 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.

—

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.

  • authlib joserfc

    • < 1.7.2affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:13joserfcfrom 0—
Debian:14joserfcbefore 1.7.2-11.7.2-1
openSUSE:Leap 16.0python-joserfcbefore 1.1.0-bp160.4.11.1.0-bp160.4.1
openSUSE:Tumbleweedpython-joserfcbefore 1.7.4-2.11.7.4-2.1
Red Hat:hummingbird:1jaegerbefore 0:2.20.0-0.8.hum10:2.20.0-0.8.hum1

Same product

authlib: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-102946joserfc: JWS signature verification bypass via empty signatures array in jws.deserialize_json
    36Monitor
  • CVE-2026-49852joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363)
    34Monitor
  • CVE-2026-119283joserfc: Unbounded JWE General JSON `recipients` Array Leads to CPU Exhaustion (DoS) via Repeated RSA Private-Key Decryption
    30Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-48990Jun 17, 2026 · joserfc: b64=false RFC7797 JWS payloads bypass JWSRegistry payload-size limits during deserialization
    21Monitor
  • Later →CVE-2026-75509Aug 24, 2026 · joserfc claim-validation bypass via array-typed single-string claims (iss/sub/jti)
    26Monitor
  • Later →CVE-2026-119284Oct 29, 2026 · joserfc: Compact JWS size guard allocates attacker-controlled segments before rejection
    27Monitor

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
authlib joserfc1.7.2 · descriptionVendor (CNA)
debian:joserfc1.7.2-1 · Debian:14Package registry (OSV)
opensuse:python-joserfc1.7.4-2.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:jaeger0:2.20.0-0.8.hum1 · Red Hat:hummingbird:1Package 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

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

Weakness class (CWE)

CWE-345 · Insufficient Verification of Data Authenticity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records