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High, CVSS 8.2amended

cryptography Vulnerable to a Subgroup Attack Due to Missing Subgroup Validation for SECT Curves

CVE-2026-26007GHSA-r6ph-v2qm-q3c2

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (cryptography 46.0.5), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.2 · CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/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 · score source
EPSS
  • CVE-2026-26007: 0.39% estimated exploitation activity in the next 30 days; percentile 33.14 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Vulnerability Summary The publickeyfromnumbers (or EllipticCurvePublicNumbers.publickey()), EllipticCurvePublicNumbers.publickey(), loadderpublickey() and loadpempublickey() functions do not verify that the point belongs to the expected prime-order subgroup of the curve. This missing validation allows an attacker to provide a public key point P from a small-order subgroup. This can lead to security issues in various situations, such as the most commonly used signature verification (ECDSA) and shared key negotiation (ECDH). When the victim computes the shared secret as S = [victimprivatekey]P via ECDH, this leaks information about victimprivatekey mod (smallsubgrouporder). For curves with cofactor 1, this reveals the least significant bits of the private key. When these weak public keys are used in ECDSA , it's easy to forge signatures on the small subgroup. Only SECT curves are impacted by this. Credit This vulnerability was discovered by: - XlabAI Team of Tencent Xuanwu Lab - Atuin…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-r6ph-v2qm-q3c2

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-r6ph-v2qm-q3c2

Agent brief

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# Patch Next advisory brief: CVE-2026-26007

Advisory: cryptography Vulnerable to a Subgroup Attack Due to Missing Subgroup Validation for SECT Curves
IDs: CVE-2026-26007, GHSA-r6ph-v2qm-q3c2
Record: https://patchnext.com/advisories/cve-2026-26007 (revision 3, source checked 26 Oct 2026, 13:36 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: cryptography 46.0.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI cryptography: affected <= 46.0.4; fixed in 46.0.5

## Suggested inspection (read-only)
- `python -m pip show cryptography`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on cryptography.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-r6ph-v2qm-q3c2 (OSV record GHSA-r6ph-v2qm-q3c2 lists affected ranges: PyPI cryptography >=0 <46.0.5 (fixed))
- Verified: https://github.com/advisories/GHSA-r6ph-v2qm-q3c2 (GitHub-reviewed advisory GHSA-r6ph-v2qm-q3c2 lists affected ranges: PyPI cryptography >=0 <=46.0.4)

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