medium CVSS 6.5 EPSS 0.34%

CVE-2026-26007·Python vulnerability

cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. Prior to 46.0.5, the public_key_from_numbers (or EllipticCurvePublicNumbers.public_key()), EllipticCurvePublicNumbers.public_key(), load_der_public_key() and load_pem_public_key() 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 = [victim_private_key]P via ECDH, this leaks information about victim_private_key mod (small_subgroup_order). 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. This vulnerability is fixed in 46.0.5.

Severity
medium
Software
Python
Fixed in
46.0.5
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.34% — higher than 27% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Affected versions

Until: 46.0.5

Fixed in: 46.0.5

How to fix this CVE

Update the Python cryptography library to version 46.0.5 or later to patch the elliptic curve point validation vulnerability. This fix ensures that public key points are verified to belong to the correct prime-order subgroup, preventing information leakage during ECDH key exchanges and signature forgery in ECDSA operations. Apply this update across all systems using cryptography for elliptic curve operations, particularly those handling SECT curves.

sudo dnf update python3-cryptography

Defensia detects this vulnerability

How to check if you are affected

  1. Run `python3 -c "import cryptography; print(cryptography.__version__)"` to check the installed cryptography library version
  2. Verify if the system uses elliptic curve cryptography by searching application code: `grep -r "EllipticCurve\|load_der_public_key\|load_pem_public_key" /path/to/application`
  3. Check application logs for ECDH key exchanges or ECDSA signature operations that might have processed untrusted public keys
  4. After patching, re-run the version check to confirm cryptography is updated to 46.0.5 or newer

FAQ

What is CVE-2026-26007?

CVE-2026-26007 is a vulnerability in Python's cryptography library where elliptic curve public key functions fail to validate that key points belong to the correct subgroup, allowing attackers to use crafted weak keys to leak private key information or forge signatures.

Is CVE-2026-26007 being actively exploited?

No, CVE-2026-26007 is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are currently available, though the vulnerability requires proper defensive measures given its cryptographic nature.

What versions of Python are affected by CVE-2026-26007?

All versions of the cryptography library prior to 46.0.5 are affected. The vulnerability impacts any application using cryptography for elliptic curve operations, regardless of the Python version.

How do I check if my server is vulnerable to CVE-2026-26007?

Execute `python3 -m pip show cryptography | grep Version` and compare the version number against 46.0.5; versions below this threshold are vulnerable.

Does Defensia detect CVE-2026-26007?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the cryptography library is installed on a monitored server, CVE-2026-26007 will appear in your dashboard with remediation steps.

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References

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