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Fencer Vulns
high 7.5

CVE-2026-4602 json

jsrsasign: Negative Exponent Handling Leads to Signature Verification Bypass

published 2026-03-23 7 mo ago modified 2026-09-10 59 d ago also GHSA-8qwj-4jxw-m8jw , EUVD-2026-14379

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 43%
public exploits
0
none known

Summary

Versions of the package jsrsasign before 11.1.1 are vulnerable to Incorrect Conversion between Numeric Types due to handling negative exponents in ext/jsbn2.js. An attacker can force the computation of incorrect modular inverses and break signature verification by calling modPow with a negative exponent.

Patch / fix

  • npm jsrsasign 11.1.1
  • n/a jsrsasign 11.1.1
  • Red Hat Migration Toolkit for Virtualization 2.1 1779139872
  • Red Hat Migration Toolkit for Virtualization 2.9 1778927462
  • Red Hat Red Hat Quay 3.10 1775169155
  • Red Hat Red Hat Quay 3.12 1775253092
  • Red Hat Red Hat Quay 3.15 1775169219
  • Red Hat Red Hat Quay 3.16 1779204086
  • Red Hat Red Hat Quay 3.9 1775169218

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-4602 updated cvss 7.5

jsrsasign: jsrsasign: Signature verification bypass via negative exponent handling

  • Red Hat Migration Toolkit for Virtualization mtv-candidate/mtv-console-plugin-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Migration Toolkit for Virtualization 2.9 migration-toolkit-virtualization 1778927462
    fixed: vendor fix RHSA-2026:19410
  • Red Hat Migration Toolkit for Virtualization 2.10 migration-toolkit-virtualization 1779139872
    fixed: vendor fix RHSA-2026:19409
  • Red Hat Quay 3.9 quay 1775169218
    fixed: vendor fix RHSA-2026:6926
  • Red Hat Quay 3.10 quay 1775169155
    fixed: vendor fix RHSA-2026:6912
  • Red Hat Quay 3.12 quay 1775253092
    fixed: vendor fix RHSA-2026:6720
  • Red Hat Quay 3.15 quay 1775169219
    fixed: vendor fix RHSA-2026:6568
  • Red Hat Quay 3.16 quay 1779204086
    fixed: vendor fix RHSA-2026:19375
show 1 more
  • Red Hat Migration Toolkit for Virtualization 2.9 migration-toolkit-virtualization 1779084876, migration-toolkit-virtualization 1779085127, migration-toolkit-virtualization 1779085283, migration-toolkit-virtualization 1779085438, migration-toolkit-virtualization 1779085916, migration-toolkit-virtualization 1779085935, +5 more Red Hat Migration Toolkit for Virtualization 2.10 migration-toolkit-virtualization 1779138168, migration-toolkit-virtualization 1779138199, migration-toolkit-virtualization 1779138211, migration-toolkit-virtualization 1779138271, migration-toolkit-virtualization 1779138320, migration-toolkit-virtualization 1779138332, +7 more Red Hat Quay 3.9 quay 1774885670, quay 1774885680, quay 1774885682, quay 1774885717, quay 1774885725, quay 1774886457, +3 more Red Hat Quay 3.10 quay 1774885559, quay 1774885579, quay 1774885592, quay 1774885636, quay 1774885638, quay 1774886143, +1 more Red Hat Quay 3.12 quay 1774885546, quay 1774885564, quay 1774885572, quay 1774885604, quay 1774885641, quay 1774886107, +3 more Red Hat Quay 3.15 quay 1774979159, quay 1774979227, quay 1774980222, quay 1774980224, quay 1774984603, quay 1775183105, +3 more
    +1 more products
    Red Hat Quay 3.16 quay 1778704509, quay 1778704515, quay 1778704550, quay 1778704556, quay 1778705015, quay 1778705065, +3 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 43% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • gist.github.com https://gist.github.com/Kr0emer/7ecd2be7d17419e4677315ef3758faf5 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CNA 4.0 7.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/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
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm jsrsasign
<11.1.1
11.1.1

Affected products

  • n/a jsrsasign
  • n/a org.webjars.npm:jsrsasign
  • Red Hat Migration Toolkit for Virtualization 2.1
  • Red Hat Migration Toolkit for Virtualization 2.9
  • Red Hat Red Hat Quay 3.10
  • Red Hat Red Hat Quay 3.12
  • Red Hat Red Hat Quay 3.15
  • Red Hat Red Hat Quay 3.16
  • Red Hat Red Hat Quay 3.9

Classification

Weakness
  • CWE-681 Incorrect Conversion between Numeric Types

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.